diff --git a/streams_map.go b/streams_map.go
new file mode 100644
index 00000000..da36dbc1
--- /dev/null
+++ b/streams_map.go
@@ -0,0 +1,59 @@
+package quic
+
+import (
+	"fmt"
+	"sync"
+
+	"github.com/lucas-clemente/quic-go/protocol"
+)
+
+type streamsMap struct {
+	streams  map[protocol.StreamID]*stream
+	nStreams int
+	mutex    sync.RWMutex
+}
+
+func newStreamsMap() *streamsMap {
+	return &streamsMap{
+		streams: map[protocol.StreamID]*stream{},
+	}
+}
+
+func (m *streamsMap) GetStream(id protocol.StreamID) (*stream, error) {
+	m.mutex.RLock()
+	s, ok := m.streams[id]
+	m.mutex.RUnlock()
+	if !ok {
+		return nil, fmt.Errorf("unknown stream: %d", id)
+	}
+	return s, nil
+}
+
+func (m *streamsMap) PutStream(s *stream) error {
+	m.mutex.Lock()
+	defer m.mutex.Unlock()
+	if _, ok := m.streams[s.StreamID()]; ok {
+		return fmt.Errorf("a stream with ID %d already exists", s.StreamID())
+	}
+	m.streams[s.StreamID()] = s
+	m.nStreams++
+	return nil
+}
+
+func (m *streamsMap) RemoveStream(id protocol.StreamID) error {
+	m.mutex.Lock()
+	defer m.mutex.Unlock()
+	s, ok := m.streams[id]
+	if !ok || s == nil {
+		return fmt.Errorf("attempted to remove non-existing stream: %d", id)
+	}
+	m.streams[id] = nil
+	m.nStreams--
+	return nil
+}
+
+func (m *streamsMap) NumberOfStreams() int {
+	m.mutex.RLock()
+	defer m.mutex.RUnlock()
+	return m.nStreams
+}
diff --git a/streams_map_test.go b/streams_map_test.go
new file mode 100644
index 00000000..725a092c
--- /dev/null
+++ b/streams_map_test.go
@@ -0,0 +1,60 @@
+package quic
+
+import (
+	"github.com/lucas-clemente/quic-go/protocol"
+	. "github.com/onsi/ginkgo"
+	. "github.com/onsi/gomega"
+)
+
+var _ = Describe("Streams Map", func() {
+	var (
+		m *streamsMap
+	)
+
+	BeforeEach(func() {
+		m = newStreamsMap()
+	})
+
+	It("returns an error for non-existant streams", func() {
+		_, err := m.GetStream(1)
+		Expect(err).To(MatchError("unknown stream: 1"))
+	})
+
+	It("returns nil for previously existing streams", func() {
+		err := m.PutStream(&stream{streamID: 1})
+		Expect(err).NotTo(HaveOccurred())
+		err = m.RemoveStream(1)
+		Expect(err).NotTo(HaveOccurred())
+		s, err := m.GetStream(1)
+		Expect(err).NotTo(HaveOccurred())
+		Expect(s).To(BeNil())
+	})
+
+	It("errors when removing non-existing stream", func() {
+		err := m.RemoveStream(1)
+		Expect(err).To(MatchError("attempted to remove non-existing stream: 1"))
+	})
+
+	It("stores streams", func() {
+		err := m.PutStream(&stream{streamID: 5})
+		Expect(err).NotTo(HaveOccurred())
+		s, err := m.GetStream(5)
+		Expect(err).NotTo(HaveOccurred())
+		Expect(s.streamID).To(Equal(protocol.StreamID(5)))
+	})
+
+	It("does not store multiple streams with the same ID", func() {
+		err := m.PutStream(&stream{streamID: 5})
+		Expect(err).NotTo(HaveOccurred())
+		err = m.PutStream(&stream{streamID: 5})
+		Expect(err).To(MatchError("a stream with ID 5 already exists"))
+	})
+
+	It("gets the number of streams", func() {
+		Expect(m.NumberOfStreams()).To(Equal(0))
+		m.PutStream(&stream{streamID: 5})
+		Expect(m.NumberOfStreams()).To(Equal(1))
+		m.RemoveStream(5)
+		Expect(m.NumberOfStreams()).To(Equal(0))
+	})
+})