diff --git a/usr/austin/eval/decls.go b/usr/austin/eval/decls.go
index c614e11bdbc..068acf92bd5 100644
--- a/usr/austin/eval/decls.go
+++ b/usr/austin/eval/decls.go
@@ -151,6 +151,23 @@ type SliceValue interface {
 	Set(Slice);
 }
 
+type Map interface {
+	Len() int64;
+	// Retrieve an element from the map, returning nil if it does
+	// not exist.
+	Elem(key interface{}) Value;
+	// Set an entry in the map.  If val is nil, delete the entry.
+	SetElem(key interface{}, val Value);
+	// TODO(austin)  Perhaps there should be an iterator interface instead.
+	Iter(func(key interface{}, val Value) bool);
+}
+
+type MapValue interface {
+	Value;
+	Get() Map;
+	Set(Map);
+}
+
 /*
  * Scopes
  */
diff --git a/usr/austin/eval/expr.go b/usr/austin/eval/expr.go
index f2f4fe21b45..024d574f561 100644
--- a/usr/austin/eval/expr.go
+++ b/usr/austin/eval/expr.go
@@ -38,7 +38,11 @@ type exprCompiler struct {
 	evalPtr func(f *Frame) Value;
 	evalFunc func(f *Frame) Func;
 	evalSlice func(f *Frame) Slice;
+	evalMap func(f *Frame) Map;
 	evalMulti func(f *Frame) []Value;
+	// Map index expressions permit special forms of assignment,
+	// for which we need to know the Map and key.
+	evalMapValue func(f *Frame) (Map, interface{});
 	// Evaluate to the "address of" this value; that is, the
 	// settable Value object.  nil for expressions whose address
 	// cannot be taken.
@@ -172,6 +176,13 @@ func (a *exprCompiler) asSlice() (func(f *Frame) Slice) {
 	return a.evalSlice;
 }
 
+func (a *exprCompiler) asMap() (func(f *Frame) Map) {
+	if a.evalMap == nil {
+		log.Crashf("tried to get %v node as MapType", a.t);
+	}
+	return a.evalMap;
+}
+
 func (a *exprCompiler) asMulti() (func(f *Frame) []Value) {
 	if a.evalMulti == nil {
 		log.Crashf("tried to get %v node as MultiType", a.t);
@@ -179,6 +190,38 @@ func (a *exprCompiler) asMulti() (func(f *Frame) []Value) {
 	return a.evalMulti;
 }
 
+func (a *exprCompiler) asInterface() (func(f *Frame) interface {}) {
+	switch _ := a.t.lit().(type) {
+	case *boolType:
+		sf := a.asBool();
+		return func(f *Frame) interface {} { return sf(f) };
+	case *uintType:
+		sf := a.asUint();
+		return func(f *Frame) interface {} { return sf(f) };
+	case *intType:
+		sf := a.asInt();
+		return func(f *Frame) interface {} { return sf(f) };
+	case *floatType:
+		sf := a.asFloat();
+		return func(f *Frame) interface {} { return sf(f) };
+	case *stringType:
+		sf := a.asString();
+		return func(f *Frame) interface {} { return sf(f) };
+	case *PtrType:
+		sf := a.asPtr();
+		return func(f *Frame) interface {} { return sf(f) };
+	case *FuncType:
+		sf := a.asFunc();
+		return func(f *Frame) interface {} { return sf(f) };
+	case *MapType:
+		sf := a.asMap();
+		return func(f *Frame) interface {} { return sf(f) };
+	default:
+		log.Crashf("unexpected expression node type %v at %v", a.t, a.pos);
+	}
+	panic();
+}
+
 /*
  * Common expression manipulations
  */
@@ -289,6 +332,10 @@ type assignCompiler struct {
 	rmt *MultiType;
 	// Whether this is an unpack assignment (case 3).
 	isUnpack bool;
+	// Whether map special assignment forms are allowed.
+	allowMap bool;
+	// Whether this is a "r, ok = a[x]" assignment.
+	isMapUnpack bool;
 	// The operation name to use in error messages, such as
 	// "assignment" or "function call".
 	errOp string;
@@ -343,6 +390,17 @@ func (a *compiler) checkAssign(pos token.Position, rs []*exprCompiler, errOp, er
 	return c, ok;
 }
 
+func (a *assignCompiler) allowMapForms(nls int) {
+	a.allowMap = true;
+
+	// Update unpacking info if this is r, ok = a[x]
+	if nls == 2 && len(a.rs) == 1 && a.rs[0].evalMapValue != nil {
+		a.isUnpack = true;
+		a.rmt = NewMultiType([]Type {a.rs[0].t, BoolType});
+		a.isMapUnpack = true;
+	}
+}
+
 // compile type checks and compiles an assignment operation, returning
 // a function that expects an l-value and the frame in which to
 // evaluate the RHS expressions.  The l-value must have exactly the
@@ -390,10 +448,25 @@ func (a *assignCompiler) compile(lt Type) (func(lv Value, f *Frame)) {
 		bc := a.rs[0].block;
 		temp := bc.DefineSlot(a.rmt);
 		tempIdx := temp.Index;
-		rf := a.rs[0].asMulti();
-		effect = func(f *Frame) {
-			f.Vars[tempIdx] = multiV(rf(f));
-		};
+		if a.isMapUnpack {
+			rf := a.rs[0].evalMapValue;
+			vt := a.rmt.Elems[0];
+			effect = func(f *Frame) {
+				m, k := rf(f);
+				v := m.Elem(k);
+				found := boolV(true);
+				if v == nil {
+					found = boolV(false);
+					v = vt.Zero();
+				}
+				f.Vars[tempIdx] = multiV([]Value {v, &found});
+			};
+		} else {
+			rf := a.rs[0].asMulti();
+			effect = func(f *Frame) {
+				f.Vars[tempIdx] = multiV(rf(f));
+			};
+		}
 		orig := a.rs[0];
 		a.rs = make([]*exprCompiler, len(a.rmt.Elems));
 		for i, t := range a.rmt.Elems {
@@ -409,9 +482,7 @@ func (a *assignCompiler) compile(lt Type) (func(lv Value, f *Frame)) {
 	// Now len(a.rs) == len(a.rmt) and we've reduced any unpacking
 	// to multi-assignment.
 
-	// TODO(austin) Deal with assignment special cases.  This is
-	// tricky in the unpack case, since some of the conversions
-	// can apply to single types within the multi-type.
+	// TODO(austin) Deal with assignment special cases.
 
 	// Values of any type may always be assigned to variables of
 	// compatible static type.
@@ -800,9 +871,18 @@ func (a *exprCompiler) DoIndexExpr(x *ast.IndexExpr) {
 		at = Uint8Type;
 		intIndex = true;
 
-	// TODO(austin) Uncomment when there is a MapType
-	// case *MapType:
-	// 	log.Crash("Index into map not implemented");
+	case *MapType:
+		at = lt.Elem;
+		if r.t.isIdeal() {
+			r = r.convertTo(lt.Key);
+			if r == nil {
+				return;
+			}
+		}
+		if !lt.Key.compat(r.t, false) {
+			a.diag("cannot use %s as index into %s", r.t, lt);
+			return;
+		}
 
 	default:
 		a.diag("cannot index into %v", l.t);
@@ -846,6 +926,7 @@ func (a *exprCompiler) DoIndexExpr(x *ast.IndexExpr) {
 	}
 
 	a.t = at;
+	a.desc = "index expression";
 
 	// Compile
 	switch lt := l.t.lit().(type) {
@@ -860,6 +941,7 @@ func (a *exprCompiler) DoIndexExpr(x *ast.IndexExpr) {
 
 	case *SliceType:
 		// TODO(austin) Bounds check
+		// TODO(austin) Can this be done with genValue?
 		a.genIndexSlice(l, r);
 		lf := l.asSlice();
 		rf := r.asInt();
@@ -877,8 +959,29 @@ func (a *exprCompiler) DoIndexExpr(x *ast.IndexExpr) {
 			return uint64(lf(f)[rf(f)]);
 		}
 
+	case *MapType:
+		// TODO(austin) Bounds check
+		lf := l.asMap();
+		rf := r.asInterface();
+		a.genValue(func(f *Frame) Value {
+			m := lf(f);
+			k := rf(f);
+			e := m.Elem(k);
+			if e == nil {
+				// TODO(austin) Use an exception
+				panic("key ", k, " not found in map");
+			}
+			return e;
+		});
+		// genValue makes things addressable, but map values
+		// aren't addressable.
+		a.evalAddr = nil;
+		a.evalMapValue = func(f *Frame) (Map, interface{}) {
+			return lf(f), rf(f);
+		};
+
 	default:
-		log.Crashf("Compilation of index into %T not implemented", l.t);
+		log.Crashf("unexpected left operand type %T", l.t.lit());
 	}
 }
 
@@ -1131,6 +1234,7 @@ func (a *exprCompiler) doBinaryExpr(op token.Token, l, r *exprCompiler) {
 	}
 
 	// Useful type predicates
+	// TODO(austin) CL 33668 mandates identical types except for comparisons.
 	compat := func() bool {
 		return l.t.compat(r.t, false);
 	};
@@ -1655,6 +1759,9 @@ func (a *exprCompiler) genConstant(v Value) {
 	case *SliceType:
 		val := v.(SliceValue).Get();
 		a.evalSlice = func(f *Frame) Slice { return val };
+	case *MapType:
+		val := v.(MapValue).Get();
+		a.evalMap = func(f *Frame) Map { return val };
 	default:
 		log.Crashf("unexpected constant type %v at %v", a.t, a.pos);
 	}
@@ -1683,6 +1790,8 @@ func (a *exprCompiler) genIdentOp(level int, index int) {
 		a.evalFunc = func(f *Frame) Func { return f.Get(level, index).(FuncValue).Get() };
 	case *SliceType:
 		a.evalSlice = func(f *Frame) Slice { return f.Get(level, index).(SliceValue).Get() };
+	case *MapType:
+		a.evalMap = func(f *Frame) Map { return f.Get(level, index).(MapValue).Get() };
 	default:
 		log.Crashf("unexpected identifier type %v at %v", a.t, a.pos);
 	}
@@ -1712,6 +1821,8 @@ func (a *exprCompiler) genIndexArray(l *exprCompiler, r *exprCompiler) {
 		a.evalFunc = func(f *Frame) Func { return lf(f).Elem(rf(f)).(FuncValue).Get() };
 	case *SliceType:
 		a.evalSlice = func(f *Frame) Slice { return lf(f).Elem(rf(f)).(SliceValue).Get() };
+	case *MapType:
+		a.evalMap = func(f *Frame) Map { return lf(f).Elem(rf(f)).(MapValue).Get() };
 	default:
 		log.Crashf("unexpected result type %v at %v", a.t, a.pos);
 	}
@@ -1741,6 +1852,8 @@ func (a *exprCompiler) genIndexSlice(l *exprCompiler, r *exprCompiler) {
 		a.evalFunc = func(f *Frame) Func { return lf(f).Base.Elem(rf(f)).(FuncValue).Get() };
 	case *SliceType:
 		a.evalSlice = func(f *Frame) Slice { return lf(f).Base.Elem(rf(f)).(SliceValue).Get() };
+	case *MapType:
+		a.evalMap = func(f *Frame) Map { return lf(f).Base.Elem(rf(f)).(MapValue).Get() };
 	default:
 		log.Crashf("unexpected result type %v at %v", a.t, a.pos);
 	}
@@ -1769,6 +1882,8 @@ func (a *exprCompiler) genFuncCall(call func(f *Frame) []Value) {
 		a.evalFunc = func(f *Frame) Func { return call(f)[0].(FuncValue).Get() };
 	case *SliceType:
 		a.evalSlice = func(f *Frame) Slice { return call(f)[0].(SliceValue).Get() };
+	case *MapType:
+		a.evalMap = func(f *Frame) Map { return call(f)[0].(MapValue).Get() };
 	case *MultiType:
 		a.evalMulti = func(f *Frame) []Value { return call(f) };
 	default:
@@ -1799,6 +1914,8 @@ func (a *exprCompiler) genValue(vf func(*Frame) Value) {
 		a.evalFunc = func(f *Frame) Func { return vf(f).(FuncValue).Get() };
 	case *SliceType:
 		a.evalSlice = func(f *Frame) Slice { return vf(f).(SliceValue).Get() };
+	case *MapType:
+		a.evalMap = func(f *Frame) Map { return vf(f).(MapValue).Get() };
 	default:
 		log.Crashf("unexpected result type %v at %v", a.t, a.pos);
 	}
@@ -2277,6 +2394,10 @@ func (a *exprCompiler) genBinOpEql(l *exprCompiler, r *exprCompiler) {
 		lf := l.asFunc();
 		rf := r.asFunc();
 		a.evalBool = func(f *Frame) bool { return lf(f) == rf(f) };
+	case *MapType:
+		lf := l.asMap();
+		rf := r.asMap();
+		a.evalBool = func(f *Frame) bool { return lf(f) == rf(f) };
 	default:
 		log.Crashf("unexpected left operand type %v at %v", l.t, a.pos);
 	}
@@ -2322,6 +2443,10 @@ func (a *exprCompiler) genBinOpNeq(l *exprCompiler, r *exprCompiler) {
 		lf := l.asFunc();
 		rf := r.asFunc();
 		a.evalBool = func(f *Frame) bool { return lf(f) != rf(f) };
+	case *MapType:
+		lf := l.asMap();
+		rf := r.asMap();
+		a.evalBool = func(f *Frame) bool { return lf(f) != rf(f) };
 	default:
 		log.Crashf("unexpected left operand type %v at %v", l.t, a.pos);
 	}
@@ -2359,6 +2484,9 @@ func genAssign(lt Type, r *exprCompiler) (func(lv Value, f *Frame)) {
 	case *SliceType:
 		rf := r.asSlice();
 		return func(lv Value, f *Frame) { lv.(SliceValue).Set(rf(f)) };
+	case *MapType:
+		rf := r.asMap();
+		return func(lv Value, f *Frame) { lv.(MapValue).Set(rf(f)) };
 	default:
 		log.Crashf("unexpected left operand type %v at %v", lt, r.pos);
 	}
diff --git a/usr/austin/eval/stmt.go b/usr/austin/eval/stmt.go
index 08c0c6d6d94..c39beeb7eb8 100644
--- a/usr/austin/eval/stmt.go
+++ b/usr/austin/eval/stmt.go
@@ -301,7 +301,7 @@ func (a *stmtCompiler) DoDeclStmt(s *ast.DeclStmt) {
 						lhs[i] = n;
 					}
 					a.doAssign(lhs, spec.Values, decl.Tok, spec.Type);
-					// TODO(austin) This is rediculous.  doAssign
+					// TODO(austin) This is ridiculous.  doAssign
 					// indicates failure by setting a.err.
 					if a.err {
 						ok = false;
@@ -454,6 +454,7 @@ func (a *stmtCompiler) doAssign(lhs []ast.Expr, rhs []ast.Expr, tok token.Token,
 	if !ok {
 		bad = true;
 	}
+	ac.allowMapForms(len(lhs));
 
 	// If this is a definition and the LHS is too big, we won't be
 	// able to produce the usual error message because we can't
@@ -560,7 +561,27 @@ func (a *stmtCompiler) doAssign(lhs []ast.Expr, rhs []ast.Expr, tok token.Token,
 			continue;
 		}
 
-		if ls[i].evalAddr == nil {
+		if ls[i].evalMapValue != nil {
+			// Map indexes are not generally addressable,
+			// but they are assignable.  If function call
+			// compiling took semantic values, this might
+			// be easier to implement as a function call.
+			sub := ls[i];
+			ls[i] = sub.copy();
+			ls[i].t, ls[i].desc = sub.t, sub.desc;
+			ls[i].evalMapValue = sub.evalMapValue;
+			mvf := sub.evalMapValue;
+			et := sub.t;
+			ls[i].evalAddr = func(f *Frame) Value {
+				m, k := mvf(f);
+				e := m.Elem(k);
+				if e == nil {
+					e = et.Zero();
+					m.SetElem(k, e);
+				}
+				return e;
+			};
+		} else if ls[i].evalAddr == nil {
 			ls[i].diag("cannot assign to %s", ls[i].desc);
 			bad = true;
 			continue;
@@ -580,6 +601,12 @@ func (a *stmtCompiler) doAssign(lhs []ast.Expr, rhs []ast.Expr, tok token.Token,
 		return;
 	}
 
+	// Check for 'a[x] = r, ok'
+	if len(ls) == 1 && len(rs) == 2 && ls[0].evalMapValue != nil {
+		a.diag("a[x] = r, ok form not implemented");
+		return;
+	}
+
 	// Create assigner
 	var lt Type;
 	n := len(lhs);
diff --git a/usr/austin/eval/type.go b/usr/austin/eval/type.go
index fd392e30c19..c0c58532e26 100644
--- a/usr/austin/eval/type.go
+++ b/usr/austin/eval/type.go
@@ -124,7 +124,7 @@ type boolType struct {
 	commonType;
 }
 
-var BoolType = universe.DefineType("bool", universePos, &boolType{});
+var BoolType = universe.DefineType("bool", universePos, &boolType{})
 
 func (t *boolType) compat(o Type, conv bool) bool {
 	t2, ok := o.lit().(*boolType);
@@ -410,10 +410,10 @@ func (t *floatType) Zero() Value {
 	panic("unexpected float bit count: ", t.Bits);
 }
 
-var maxFloat32Val = bignum.MakeRat(bignum.Int(0xffffff).Shl(127-23), bignum.Nat(1));
-var maxFloat64Val = bignum.MakeRat(bignum.Int(0x1fffffffffffff).Shl(1023-52), bignum.Nat(1));
-var minFloat32Val = maxFloat32Val.Neg();
-var minFloat64Val = maxFloat64Val.Neg();
+var maxFloat32Val = bignum.MakeRat(bignum.Int(0xffffff).Shl(127-23), bignum.Nat(1))
+var maxFloat64Val = bignum.MakeRat(bignum.Int(0x1fffffffffffff).Shl(1023-52), bignum.Nat(1))
+var minFloat32Val = maxFloat32Val.Neg()
+var minFloat64Val = maxFloat64Val.Neg()
 
 func (t *floatType) minVal() *bignum.Rational {
 	bits := t.Bits;
@@ -488,7 +488,7 @@ type stringType struct {
 	commonType;
 }
 
-var StringType = universe.DefineType("string", universePos, &stringType{});
+var StringType = universe.DefineType("string", universePos, &stringType{})
 
 func (t *stringType) compat(o Type, conv bool) bool {
 	t2, ok := o.lit().(*stringType);
@@ -518,7 +518,7 @@ type ArrayType struct {
 	Elem Type;
 }
 
-var arrayTypes = make(map[int64] map[Type] *ArrayType);
+var arrayTypes = make(map[int64] map[Type] *ArrayType)
 
 // Two array types are identical if they have identical element types
 // and the same array length.
@@ -732,8 +732,8 @@ type FuncType struct {
 	Out []Type;
 }
 
-var funcTypes = newTypeArrayMap();
-var variadicFuncTypes = newTypeArrayMap();
+var funcTypes = newTypeArrayMap()
+var variadicFuncTypes = newTypeArrayMap()
 
 // Two function types are identical if they have the same number of
 // parameters and result values and if corresponding parameter and
@@ -898,10 +898,52 @@ func (t *SliceType) Zero() Value {
 }
 
 /*
+ * Map type
+ */
+
 type MapType struct {
-	// TODO(austin)
+	commonType;
+	Key Type;
+	Elem Type;
 }
 
+var mapTypes = make(map[Type] map[Type] *MapType)
+
+func NewMapType(key Type, elem Type) *MapType {
+	ts, ok := mapTypes[key];
+	if !ok {
+		ts = make(map[Type] *MapType);
+		mapTypes[key] = ts;
+	}
+	t, ok := ts[elem];
+	if !ok {
+		t = &MapType{commonType{}, key, elem};
+		ts[elem] = t;
+	}
+	return t;
+}
+
+func (t *MapType) compat(o Type, conv bool) bool {
+	t2, ok := o.lit().(*MapType);
+	if !ok {
+		return false;
+	}
+	return t.Elem.compat(t2.Elem, conv) && t.Key.compat(t2.Key, conv);
+}
+
+func (t *MapType) lit() Type {
+	return t;
+}
+
+func (t *MapType) String() string {
+	return "map[" + t.Key.String() + "] " + t.Elem.String();
+}
+
+func (t *MapType) Zero() Value {
+	return &mapV{nil};
+}
+
+/*
 type ChanType struct {
 	// TODO(austin)
 }
@@ -1016,7 +1058,7 @@ func (t *MultiType) compat(o Type, conv bool) bool {
 	return true;
 }
 
-var EmptyType Type = NewMultiType([]Type{});
+var EmptyType Type = NewMultiType([]Type{})
 
 func (t *MultiType) lit() Type {
 	return t;
diff --git a/usr/austin/eval/typec.go b/usr/austin/eval/typec.go
index 883950baab9..3a9fd0c45b0 100644
--- a/usr/austin/eval/typec.go
+++ b/usr/austin/eval/typec.go
@@ -233,6 +233,28 @@ func (a *typeCompiler) compileFuncType(x *ast.FuncType, allowRec bool) *FuncDecl
 	return &FuncDecl{NewFuncType(in, false, out), nil, inNames, outNames};
 }
 
+func (a *typeCompiler) compileMapType(x *ast.MapType) Type {
+	key := a.compileType(x.Key, true);
+	val := a.compileType(x.Value, true);
+	if key == nil || val == nil {
+		return nil;
+	}
+	// XXX(Spec) The Map types section explicitly lists all types
+	// that can be map keys except for function types.
+	switch _ := key.lit().(type) {
+	case *StructType:
+		a.diagAt(x, "map key cannot be a struct type");
+		return nil;
+	case *ArrayType:
+		a.diagAt(x, "map key cannot be an array type");
+		return nil;
+	case *SliceType:
+		a.diagAt(x, "map key cannot be a slice type");
+		return nil;
+	}
+	return NewMapType(key, val);
+}
+
 func (a *typeCompiler) compileType(x ast.Expr, allowRec bool) Type {
 	switch x := x.(type) {
 	case *ast.BadExpr:
@@ -261,7 +283,7 @@ func (a *typeCompiler) compileType(x ast.Expr, allowRec bool) Type {
 		goto notimpl;
 
 	case *ast.MapType:
-		goto notimpl;
+		return a.compileMapType(x);
 
 	case *ast.ChanType:
 		goto notimpl;
diff --git a/usr/austin/eval/value.go b/usr/austin/eval/value.go
index 8950dd00a82..3aa23199703 100644
--- a/usr/austin/eval/value.go
+++ b/usr/austin/eval/value.go
@@ -504,6 +504,69 @@ func (v *sliceV) Set(x Slice) {
 	v.Slice = x;
 }
 
+/*
+ * Maps
+ */
+
+type mapV struct {
+	target Map;
+}
+
+func (v *mapV) String() string {
+	res := "map[";
+	i := 0;
+	v.target.Iter(func(key interface{}, val Value) bool {
+		if i > 0 {
+			res += ", ";
+		}
+		i++;
+		res += fmt.Sprint(key) + ":" + val.String();
+		return true;
+	});
+	return res + "]";
+}
+
+func (v *mapV) Assign(o Value) {
+	v.target = o.(MapValue).Get();
+}
+
+func (v *mapV) Get() Map {
+	return v.target;
+}
+
+func (v *mapV) Set(x Map) {
+	v.target = x;
+}
+
+type evalMap map[interface{}] Value
+
+func (m evalMap) Len() int64 {
+	return int64(len(m));
+}
+
+func (m evalMap) Elem(key interface{}) Value {
+	if v, ok := m[key]; ok {
+		return v;
+	}
+	return nil;
+}
+
+func (m evalMap) SetElem(key interface{}, val Value) {
+	if val == nil {
+		m[key] = nil, false;
+	} else {
+		m[key] = val;
+	}
+}
+
+func (m evalMap) Iter(cb func(key interface{}, val Value) bool) {
+	for k, v := range m {
+		if !cb(k, v) {
+			break;
+		}
+	}
+}
+
 /*
  * Multi-values
  */