diff --git a/enc/json_decode.go b/enc/json_decode.go
index f07894e514..38ddd3a559 100644
--- a/enc/json_decode.go
+++ b/enc/json_decode.go
@@ -73,6 +73,10 @@ func jsonDecodeTaggedValue(m map[string]interface{}, s store.ChunkSource) (types
 			if v, ok := v.([]interface{}); ok {
 				return jsonDecodeList(v, s)
 			}
+		case "set":
+			if v, ok := v.([]interface{}); ok {
+				return jsonDecodeSet(v, s)
+			}
 		case "map":
 			if v, ok := v.(map[string]interface{}); ok {
 				return jsonDecodeMap(v, s)
@@ -99,6 +103,18 @@ func jsonDecodeList(input []interface{}, s store.ChunkSource) (types.Value, erro
 	return output, nil
 }
 
+func jsonDecodeSet(input []interface{}, s store.ChunkSource) (types.Value, error) {
+	vals := []types.Value{}
+	for _, inVal := range input {
+		outVal, err := jsonDecodeValue(inVal, s)
+		if err != nil {
+			return nil, err
+		}
+		vals = append(vals, outVal)
+	}
+	return types.NewSet(vals...), nil
+}
+
 func jsonDecodeMap(input map[string]interface{}, s store.ChunkSource) (types.Value, error) {
 	output := types.NewMap()
 	for k, inVal := range input {
diff --git a/enc/json_decode_test.go b/enc/json_decode_test.go
index 66a0d6c5b8..34ea2b1441 100644
--- a/enc/json_decode_test.go
+++ b/enc/json_decode_test.go
@@ -70,5 +70,11 @@ func TestJSONDecode(t *testing.T) {
 	testDecode(`j {"map":{"bool":false,"int32":{"int32":42},"list":{"ref":"sha1-58bdf8e374b39f9b1e8a64784cf5c09601f4b7ea"},"map":{"ref":"sha1-fa8026bf44f60b64ab674c49cda31a697467973c"},"string":"hotdog"}}
 	//`, types.NewMap("bool", types.Bool(false), "int32", types.Int32(42), "string", types.NewString("hotdog"), "list", types.NewList(), "map", types.NewMap()))
 
+	// Sets
+	testDecode(`j {"set":[]}
+`, types.NewSet())
+	testDecode(`j {"set":[{"int32":42},"hotdog",{"ref":"sha1-58bdf8e374b39f9b1e8a64784cf5c09601f4b7ea"},false,{"ref":"sha1-fa8026bf44f60b64ab674c49cda31a697467973c"}]}
+`, types.NewSet(types.Bool(false), types.Int32(42), types.NewString("hotdog"), types.NewList(), types.NewMap()))
+
 	// referenced blobs?
 }
diff --git a/enc/json_encode.go b/enc/json_encode.go
index 3d79a206dd..912a2b1c66 100644
--- a/enc/json_encode.go
+++ b/enc/json_encode.go
@@ -3,6 +3,7 @@ package enc
 import (
 	"encoding/json"
 	"fmt"
+	"sort"
 
 	. "github.com/attic-labs/noms/dbg"
 	"github.com/attic-labs/noms/ref"
@@ -61,6 +62,8 @@ func getJSON(v types.Value, s store.ChunkSink) (interface{}, error) {
 		return getJSONList(v, s)
 	case types.Map:
 		return getJSONMap(v, s)
+	case types.Set:
+		return getJSONSet(v, s)
 	case types.String:
 		return v.String(), nil
 	case types.UInt16:
@@ -117,16 +120,46 @@ func getJSONMap(m types.Map, s store.ChunkSink) (r interface{}, err error) {
 	return
 }
 
+func getJSONSet(set types.Set, s store.ChunkSink) (r interface{}, err error) {
+	// Iteration through Set is random, but we need a deterministic order for serialization. Let's order using the refs of the values in the set.
+	lookup := map[ref.Ref]types.Value{}
+	order := ref.RefSlice{}
+	set.Iter(func(v types.Value) (stop bool) {
+		order = append(order, v.Ref())
+		lookup[v.Ref()] = v
+		return
+	})
+	sort.Sort(order)
+
+	j := []interface{}{}
+	for _, r := range order {
+		v := lookup[r]
+		var cj interface{}
+		cj, err = getChildJSON(v, s)
+		if err != nil {
+			return nil, err
+		}
+		j = append(j, cj)
+	}
+
+	r = map[string]interface{}{
+		"set": j,
+	}
+	return
+}
+
 func getChildJSON(v types.Value, s store.ChunkSink) (interface{}, error) {
 	var r ref.Ref
 	var err error
 	switch v := v.(type) {
-	// Blobs, maps, and lists are always out-of-line
+	// Blobs, lists, maps, and sets are always out-of-line
 	case types.Blob:
 		r, err = WriteValue(v, s)
+	case types.List:
+		r, err = WriteValue(v, s)
 	case types.Map:
 		r, err = WriteValue(v, s)
-	case types.List:
+	case types.Set:
 		r, err = WriteValue(v, s)
 	default:
 		// Other types are always inline.
diff --git a/enc/json_encode_test.go b/enc/json_encode_test.go
index 499e1b85f0..4fbf5ca9a6 100644
--- a/enc/json_encode_test.go
+++ b/enc/json_encode_test.go
@@ -83,4 +83,8 @@ func TestJsonEncode(t *testing.T) {
 	testEncode(`j {"map":{"bool":false,"int32":{"int32":42},"list":{"ref":"sha1-58bdf8e374b39f9b1e8a64784cf5c09601f4b7ea"},"map":{"ref":"sha1-fa8026bf44f60b64ab674c49cda31a697467973c"},"string":"hotdog"}}
 `, types.NewMap("bool", types.Bool(false), "int32", types.Int32(42), "string", types.NewString("hotdog"), "list", types.NewList(), "map", types.NewMap()))
 	assertChildVals()
+
+	// Sets
+	testEncode(`j {"set":[]}
+`, types.NewSet())
 }
diff --git a/ref/ref_slice.go b/ref/ref_slice.go
new file mode 100644
index 0000000000..7b3ab540d6
--- /dev/null
+++ b/ref/ref_slice.go
@@ -0,0 +1,43 @@
+package ref
+
+import (
+	. "github.com/attic-labs/noms/dbg"
+)
+
+type RefSlice []Ref
+
+func (rs RefSlice) Len() int {
+	return len(rs)
+}
+
+func (rs RefSlice) Less(i, j int) bool {
+	d1, d2 := rs[i].digest, rs[j].digest
+	Chk.Equal(len(d1), len(d2))
+	for k := 0; k < len(d1); k++ {
+		b1, b2 := d1[k], d2[k]
+		if b1 < b2 {
+			return true
+		} else if b1 > b2 {
+			return false
+		}
+	}
+	return false
+}
+
+func (rs RefSlice) Swap(i, j int) {
+	t := rs[j]
+	rs[j] = rs[i]
+	rs[i] = t
+}
+
+func (rs RefSlice) Equals(other RefSlice) bool {
+	if len(rs) != len(other) {
+		return false
+	}
+	for i := 0; i < len(rs); i++ {
+		if rs[i] != other[i] {
+			return false
+		}
+	}
+	return true
+}
diff --git a/ref/ref_slice_test.go b/ref/ref_slice_test.go
new file mode 100644
index 0000000000..8b8dfda820
--- /dev/null
+++ b/ref/ref_slice_test.go
@@ -0,0 +1,31 @@
+package ref
+
+import (
+	"sort"
+	"testing"
+
+	"github.com/stretchr/testify/assert"
+)
+
+func TestRefSliceSort(t *testing.T) {
+	assert := assert.New(t)
+
+	rs := RefSlice{}
+	for i := 1; i <= 3; i++ {
+		for j := 1; j <= 3; j++ {
+			d := Sha1Digest{}
+			for k := 1; k <= j; k++ {
+				d[k-1] = byte(i)
+			}
+			rs = append(rs, New(d))
+		}
+	}
+
+	rs2 := RefSlice(make([]Ref, len(rs)))
+	copy(rs2, rs)
+	sort.Sort(sort.Reverse(rs2))
+	assert.False(rs.Equals(rs2))
+
+	sort.Sort(rs2)
+	assert.True(rs.Equals(rs2))
+}
diff --git a/types/flat_map.go b/types/flat_map.go
index 691fad9c38..5ead9ce368 100644
--- a/types/flat_map.go
+++ b/types/flat_map.go
@@ -52,7 +52,7 @@ func (fm flatMap) Remove(k string) Map {
 	return newFlatMap(m)
 }
 
-func (fm flatMap) Iter(cb IterCallback) {
+func (fm flatMap) Iter(cb mapIterCallback) {
 	for k, v := range fm.m {
 		if cb(k, v) {
 			break
diff --git a/types/flat_set.go b/types/flat_set.go
new file mode 100644
index 0000000000..ff6e56257a
--- /dev/null
+++ b/types/flat_set.go
@@ -0,0 +1,77 @@
+package types
+
+import (
+	"github.com/attic-labs/noms/ref"
+)
+
+type flatSet struct {
+	m  setInternalMap
+	cr *cachedRef
+}
+
+type setInternalMap map[ref.Ref]Value
+
+func newFlatSet(m setInternalMap) flatSet {
+	return flatSet{
+		m:  m,
+		cr: &cachedRef{},
+	}
+}
+
+func (fs flatSet) Len() uint64 {
+	return uint64(len(fs.m))
+}
+
+func (fs flatSet) Has(v Value) bool {
+	_, ok := fs.m[v.Ref()]
+	return ok
+}
+
+func (fs flatSet) Insert(values ...Value) Set {
+	return newFlatSet(buildInternalMap(fs.m, values))
+}
+
+func (fs flatSet) Remove(values ...Value) Set {
+	m2 := copyInternalMap(fs.m)
+	for _, v := range values {
+		delete(m2, v.Ref())
+	}
+	return newFlatSet(m2)
+}
+
+func (fm flatSet) Iter(cb setIterCallback) {
+	// TODO: sort iteration order
+	for _, v := range fm.m {
+		if cb(v) {
+			break
+		}
+	}
+}
+
+func (fs flatSet) Ref() ref.Ref {
+	return fs.cr.Ref(fs)
+}
+
+func (fs flatSet) Equals(other Value) bool {
+	if other == nil {
+		return false
+	} else {
+		return fs.Ref() == other.Ref()
+	}
+}
+
+func copyInternalMap(m setInternalMap) setInternalMap {
+	r := setInternalMap{}
+	for k, v := range m {
+		r[k] = v
+	}
+	return r
+}
+
+func buildInternalMap(old setInternalMap, values []Value) setInternalMap {
+	m := copyInternalMap(old)
+	for _, v := range values {
+		m[v.Ref()] = v
+	}
+	return m
+}
diff --git a/types/map.go b/types/map.go
index ed441726de..2344726913 100644
--- a/types/map.go
+++ b/types/map.go
@@ -1,6 +1,6 @@
 package types
 
-type IterCallback func(k string, v Value) bool
+type mapIterCallback func(k string, v Value) bool
 
 type Map interface {
 	Value
@@ -11,7 +11,7 @@ type Map interface {
 	Set(k string, v Value) Map
 	SetM(kv ...interface{}) Map
 	Remove(k string) Map
-	Iter(IterCallback)
+	Iter(mapIterCallback)
 }
 
 func NewMap(kv ...interface{}) Map {
diff --git a/types/set.go b/types/set.go
new file mode 100644
index 0000000000..ebe975f503
--- /dev/null
+++ b/types/set.go
@@ -0,0 +1,16 @@
+package types
+
+type setIterCallback func(v Value) bool
+
+type Set interface {
+	Value
+	Len() uint64
+	Has(v Value) bool
+	Iter(setIterCallback)
+	Insert(v ...Value) Set
+	Remove(v ...Value) Set
+}
+
+func NewSet(v ...Value) Set {
+	return newFlatSet(buildInternalMap(setInternalMap{}, v))
+}
diff --git a/types/test/cached_ref_test.go b/types/test/cached_ref_test.go
index 31f4c11059..1ddb9a34f3 100644
--- a/types/test/cached_ref_test.go
+++ b/types/test/cached_ref_test.go
@@ -37,6 +37,7 @@ func TestCachedRef(t *testing.T) {
 		NewList(),
 		NewString(""),
 		NewMap(),
+		NewSet(),
 	}
 	for i := 0; i < 2; i++ {
 		for j, v := range values {
diff --git a/types/test/equals_test.go b/types/test/equals_test.go
index 3570fc5ea2..29f45f4be9 100644
--- a/types/test/equals_test.go
+++ b/types/test/equals_test.go
@@ -47,6 +47,8 @@ func TestPrimitiveEquals(t *testing.T) {
 		func() types.Value { return types.NewList(types.NewString("bar")) },
 		func() types.Value { return types.NewMap() },
 		func() types.Value { return types.NewMap("a", types.NewString("a")) },
+		func() types.Value { return types.NewSet() },
+		func() types.Value { return types.NewSet(types.NewString("hi")) },
 	}
 
 	for i, f1 := range values {
diff --git a/types/test/flat_set_test.go b/types/test/flat_set_test.go
new file mode 100644
index 0000000000..d0f4ea3a16
--- /dev/null
+++ b/types/test/flat_set_test.go
@@ -0,0 +1,82 @@
+package test
+
+import (
+	"testing"
+
+	_ "github.com/attic-labs/noms/enc"
+	. "github.com/attic-labs/noms/types"
+	"github.com/stretchr/testify/assert"
+)
+
+func TestSetLen(t *testing.T) {
+	assert := assert.New(t)
+	s1 := NewSet(Bool(true), Int32(1), NewString("hi"))
+	assert.Equal(uint64(3), s1.Len())
+	s2 := s1.Insert(Bool(false))
+	assert.Equal(uint64(4), s2.Len())
+	s3 := s2.Remove(Bool(true))
+	assert.Equal(uint64(3), s3.Len())
+}
+
+func TestSetHas(t *testing.T) {
+	assert := assert.New(t)
+	s1 := NewSet(Bool(true), Int32(1), NewString("hi"))
+	assert.True(s1.Has(Bool(true)))
+	assert.False(s1.Has(Bool(false)))
+	assert.True(s1.Has(Int32(1)))
+	assert.False(s1.Has(Int32(0)))
+	assert.True(s1.Has(NewString("hi")))
+	assert.False(s1.Has(NewString("ho")))
+
+	s2 := s1.Insert(Bool(false))
+	assert.True(s2.Has(Bool(false)))
+	assert.True(s2.Has(Bool(true)))
+
+	assert.True(s1.Has(Bool(true)))
+	assert.False(s1.Has(Bool(false)))
+}
+
+func TestSetInsert(t *testing.T) {
+	assert := assert.New(t)
+	s := NewSet()
+	v1 := Bool(false)
+	v2 := Bool(true)
+	v3 := Int32(0)
+
+	assert.False(s.Has(v1))
+	s = s.Insert(v1)
+	assert.True(s.Has(v1))
+	s = s.Insert(v2)
+	assert.True(s.Has(v1))
+	assert.True(s.Has(v2))
+	s2 := s.Insert(v3)
+	assert.True(s.Has(v1))
+	assert.True(s.Has(v2))
+	assert.False(s.Has(v3))
+	assert.True(s2.Has(v1))
+	assert.True(s2.Has(v2))
+	assert.True(s2.Has(v3))
+}
+
+func TestSetRemove(t *testing.T) {
+	assert := assert.New(t)
+	v1 := Bool(false)
+	v2 := Bool(true)
+	v3 := Int32(0)
+	s := NewSet(v1, v2, v3)
+	assert.True(s.Has(v1))
+	assert.True(s.Has(v2))
+	assert.True(s.Has(v3))
+	s = s.Remove(v1)
+	assert.False(s.Has(v1))
+	assert.True(s.Has(v2))
+	assert.True(s.Has(v3))
+	s2 := s.Remove(v2)
+	assert.False(s.Has(v1))
+	assert.True(s.Has(v2))
+	assert.True(s.Has(v3))
+	assert.False(s2.Has(v1))
+	assert.False(s2.Has(v2))
+	assert.True(s2.Has(v3))
+
+}