diff --git a/pkg/stream/set.go b/pkg/stream/set.go
index d9caa79..77de154 100644
--- a/pkg/stream/set.go
+++ b/pkg/stream/set.go
@@ -149,3 +149,107 @@ func difference[E any](s1, s2 Stream[E], kv kvstore.Maker[E, struct{}]) Stream[E
 		})
 	}
 }
+
+// SymmetricDifference returns a stream that contains elements that are in either of the given streams, but not in both.
+// The element type E must be comparable.
+// The order of the elements is not guaranteed.
+//
+// Example usage:
+//
+//	s := stream.SymmetricDifference(stream.Of(1, 2, 3, 4, 5), stream.Of(4, 5, 6))
+//	out := stream.DebugString(s) // "<1, 2, 3, 6>"
+func SymmetricDifference[E comparable](s1, s2 Stream[E]) Stream[E] {
+	return Union(Difference(s1, s2), Difference(s2, s1))
+}
+
+// SymmetricDifferenceBy returns a stream that contains elements that are in either of the given streams, but not in both, compared by the given cmp.Comparer.
+// The order of the elements is not guaranteed.
+//
+// Example usage:
+//
+//	s := stream.SymmetricDifferenceBy(stream.Of(1, 2, 3, 4, 5), stream.Of(4, 5, 6), cmp.Natural[int]())
+//	out := stream.DebugString(s) // "<1, 2, 3, 6>"
+func SymmetricDifferenceBy[E any](s1, s2 Stream[E], compare cmp.Comparer[E]) Stream[E] {
+	return Union(DifferenceBy(s1, s2, compare), DifferenceBy(s2, s1, compare))
+}
+
+// Subset returns true if all elements of the first stream are in the second stream.
+// The element type E must be comparable.
+//
+// Example usage:
+//
+//	ok := stream.Subset(stream.Of(1, 2), stream.Of(1, 2, 3, 4))
+//	fmt.Println(ok) // "true"
+func Subset[E comparable](s1, s2 Stream[E]) bool {
+	// Index elements of the second stream into a set.
+	seen := kvstore.MappedMaker[E, struct{}]()()
+	s2(func(e E) bool {
+		seen.Put(e, struct{}{})
+		return true
+	})
+	// Check if all elements of the first stream are in the set.
+	return s1(func(e E) bool {
+		return seen.Get(e).Present()
+	})
+}
+
+// SubsetBy returns true if all elements of the first stream are in the second stream, compared by the given cmp.Comparer.
+//
+// Example usage:
+//
+//	ok := stream.SubsetBy(stream.Of(1, 2), stream.Of(1, 2, 3, 4), cmp.Natural[int]())
+//	fmt.Println(ok) // "true"
+func SubsetBy[E any](s1, s2 Stream[E], compare cmp.Comparer[E]) bool {
+	// Index elements of the second stream into a set.
+	seen := kvstore.SortedMaker[E, struct{}](compare)()
+	s2(func(e E) bool {
+		seen.Put(e, struct{}{})
+		return true
+	})
+	// Check if all elements of the first stream are in the set.
+	return s1(func(e E) bool {
+		return seen.Get(e).Present()
+	})
+}
+
+// Superset returns true if all elements of the second stream are in the first stream.
+// The element type E must be comparable.
+//
+// Example usage:
+//
+//	ok := stream.Superset(stream.Of(1, 2, 3, 4), stream.Of(1, 2))
+//	fmt.Println(ok) // "true"
+func Superset[E comparable](s1, s2 Stream[E]) bool {
+	return Subset(s2, s1)
+}
+
+// SupersetBy returns true if all elements of the second stream are in the first stream, compared by the given cmp.Comparer.
+//
+// Example usage:
+//
+//	ok := stream.SupersetBy(stream.Of(1, 2, 3, 4), stream.Of(1, 2), cmp.Natural[int]())
+//	fmt.Println(ok) // "true"
+func SupersetBy[E any](s1, s2 Stream[E], compare cmp.Comparer[E]) bool {
+	return SubsetBy(s2, s1, compare)
+}
+
+// SetEqual returns true if the two streams contain the same elements (in any order).
+// The element type E must be comparable.
+//
+// Example usage:
+//
+//	ok := stream.SetEqual(stream.Of(1, 2, 3), stream.Of(3, 2, 1))
+//	fmt.Println(ok) // "true"
+func SetEqual[E comparable](s1, s2 Stream[E]) bool {
+	return Subset(s1, s2) && Subset(s2, s1)
+}
+
+// SetEqualBy returns true if the two streams contain the same elements (in any order), compared by the given cmp.Comparer.
+//
+// Example usage:
+//
+//	ok := stream.SetEqualBy(stream.Of(1, 2, 3), stream.Of(3, 2, 1), cmp.Natural[int]())
+//	fmt.Println(ok) // "true"
+func SetEqualBy[E any](s1, s2 Stream[E], compare cmp.Comparer[E]) bool {
+	return SubsetBy(s1, s2, compare) && SubsetBy(s2, s1, compare)
+}
diff --git a/pkg/stream/set_test.go b/pkg/stream/set_test.go
index b6d4d86..6d05603 100644
--- a/pkg/stream/set_test.go
+++ b/pkg/stream/set_test.go
@@ -137,19 +137,83 @@ func TestIntersectionAllBy(t *testing.T) {
 }
 
 func TestDifference(t *testing.T) {
-	t.Run("two-streams", func(t *testing.T) {
-		s := Difference(Of(1, 2, 3), Of(2, 3, 4))
-		got := CollectSlice(s)
-		want := []int{1}
-		assert.ElementsMatch(t, got, want)
-	})
+	s := Difference(Of(1, 2, 3), Of(2, 3, 4))
+	got := CollectSlice(s)
+	want := []int{1}
+	assert.ElementsMatch(t, got, want)
 }
 
 func TestDifferenceBy(t *testing.T) {
-	t.Run("two-streams", func(t *testing.T) {
-		s := DifferenceBy(Of(1, 2, 3), Of(2, 3, 4), cmp.Natural[int]())
-		got := CollectSlice(s)
-		want := []int{1}
-		assert.ElementsMatch(t, got, want)
-	})
+	s := DifferenceBy(Of(1, 2, 3), Of(2, 3, 4), cmp.Natural[int]())
+	got := CollectSlice(s)
+	want := []int{1}
+	assert.ElementsMatch(t, got, want)
+}
+
+func TestSymmetricDifference(t *testing.T) {
+	s := SymmetricDifference(Of(1, 2, 3), Of(2, 3, 4))
+	got := CollectSlice(s)
+	want := []int{1, 4}
+	assert.ElementsMatch(t, got, want)
+}
+
+func TestSymmetricDifferenceBy(t *testing.T) {
+	s := SymmetricDifferenceBy(Of(1, 2, 3), Of(2, 3, 4), cmp.Natural[int]())
+	got := CollectSlice(s)
+	want := []int{1, 4}
+	assert.ElementsMatch(t, got, want)
+}
+
+func TestSubset(t *testing.T) {
+	if Subset(Of(1, 2, 3), Of(2, 3, 4)) {
+		t.Errorf("Subset(Of(1, 2, 3), Of(2, 3, 4)) = true; want false")
+	}
+	if !Subset(Of(1, 2, 3), Of(1, 2, 3, 4)) {
+		t.Errorf("Subset(Of(1, 2, 3), Of(1, 2, 3, 4)) = false; want true")
+	}
+}
+
+func TestSubsetBy(t *testing.T) {
+	if SubsetBy(Of(1, 2, 3), Of(2, 3, 4), cmp.Natural[int]()) {
+		t.Errorf("SubsetBy(Of(1, 2, 3), Of(2, 3, 4), cmp.Natural[int]()) = true; want false")
+	}
+	if !SubsetBy(Of(1, 2, 3), Of(1, 2, 3, 4), cmp.Natural[int]()) {
+		t.Errorf("SubsetBy(Of(1, 2, 3), Of(1, 2, 3, 4), cmp.Natural[int]()) = false; want true")
+	}
+}
+
+func TestSuperset(t *testing.T) {
+	if !Superset(Of(1, 2, 3, 4), Of(2, 3)) {
+		t.Errorf("Superset(Of(1, 2, 3, 4), Of(2, 3)) = false; want true")
+	}
+	if Superset(Of(1, 2, 3, 4), Of(3, 4, 5)) {
+		t.Errorf("Superset(Of(1, 2, 3, 4), Of(3, 4, 5)) = true; want false")
+	}
+}
+
+func TestSupersetBy(t *testing.T) {
+	if !SupersetBy(Of(1, 2, 3, 4), Of(2, 3), cmp.Natural[int]()) {
+		t.Errorf("SupersetBy(Of(1, 2, 3, 4), Of(2, 3), cmp.Natural[int]()) = false; want true")
+	}
+	if SupersetBy(Of(1, 2, 3, 4), Of(3, 4, 5), cmp.Natural[int]()) {
+		t.Errorf("SupersetBy(Of(1, 2, 3, 4), Of(3, 4, 5), cmp.Natural[int]()) = true; want false")
+	}
+}
+
+func TestSetEqual(t *testing.T) {
+	if SetEqual(Of(1, 2, 3), Of(2, 3, 4)) {
+		t.Errorf("SetEqual(Of(1, 2, 3), Of(2, 3, 4)) = true; want false")
+	}
+	if !SetEqual(Of(1, 2, 3), Of(3, 2, 1)) {
+		t.Errorf("SetEqual(Of(1, 2, 3), Of(3, 2, 1)) = false; want true")
+	}
+}
+
+func TestSetEqualBy(t *testing.T) {
+	if SetEqualBy(Of(1, 2, 3), Of(2, 3, 4), cmp.Natural[int]()) {
+		t.Errorf("SetEqualBy(Of(1, 2, 3), Of(2, 3, 4), cmp.Natural[int]()) = true; want false")
+	}
+	if !SetEqualBy(Of(1, 2, 3), Of(3, 2, 1), cmp.Natural[int]()) {
+		t.Errorf("SetEqualBy(Of(1, 2, 3), Of(3, 2, 1), cmp.Natural[int]()) = false; want true")
+	}
 }