diff --git a/chat/command.go b/chat/command.go
index 536de69..63423c0 100644
--- a/chat/command.go
+++ b/chat/command.go
@@ -477,4 +477,38 @@ func InitCommands(c *Commands) {
 			return nil
 		},
 	})
+
+	c.Add(Command{
+		Op:         true,
+		Prefix:     "/mute",
+		PrefixHelp: "USER",
+		Help:       "Toggle muting USER, preventing messages from broadcasting.",
+		Handler: func(room *Room, msg message.CommandMsg) error {
+			if !room.IsOp(msg.From()) {
+				return errors.New("must be op")
+			}
+
+			args := msg.Args()
+			if len(args) == 0 {
+				return errors.New("must specify user")
+			}
+
+			member, ok := room.MemberByID(args[0])
+			if !ok {
+				return errors.New("user not found")
+			}
+
+			setMute := !member.IsMuted()
+			member.SetMute(setMute)
+			id := member.ID()
+
+			if setMute {
+				room.Send(message.NewSystemMsg("Muted: "+id, msg.From()))
+			} else {
+				room.Send(message.NewSystemMsg("Unmuted: "+id, msg.From()))
+			}
+
+			return nil
+		},
+	})
 }
diff --git a/chat/logger.go b/chat/logger.go
index 477e1d3..0f4087d 100644
--- a/chat/logger.go
+++ b/chat/logger.go
@@ -1,7 +1,9 @@
 package chat
 
-import "io"
-import stdlog "log"
+import (
+	"io"
+	stdlog "log"
+)
 
 var logger *stdlog.Logger
 
diff --git a/chat/room.go b/chat/room.go
index b126845..9539ec9 100644
--- a/chat/room.go
+++ b/chat/room.go
@@ -27,6 +27,23 @@ var ErrInvalidName = errors.New("invalid name")
 type Member struct {
 	*message.User
 	IsOp bool
+
+	// TODO: Move IsOp under mu?
+
+	mu      sync.Mutex
+	isMuted bool // When true, messages should not be broadcasted.
+}
+
+func (m *Member) IsMuted() bool {
+	m.mu.Lock()
+	defer m.mu.Unlock()
+	return m.isMuted
+}
+
+func (m *Member) SetMute(muted bool) {
+	m.mu.Lock()
+	defer m.mu.Unlock()
+	m.isMuted = muted
 }
 
 // Room definition, also a Set of User Items
@@ -84,6 +101,20 @@ func (r *Room) HandleMsg(m message.Message) {
 		fromID = fromMsg.From().ID()
 	}
 
+	if fromID != "" {
+		if item, err := r.Members.Get(fromID); err != nil {
+			// Message from a member who is not in the room, this should not happen.
+			logger.Printf("Room received unexpected message from a non-member: %v", m)
+			return
+		} else if member, ok := item.Value().(*Member); ok && member.IsMuted() {
+			// Short circuit message handling for muted users
+			if _, ok = m.(*message.CommandMsg); !ok {
+				member.User.Send(m)
+			}
+			return
+		}
+	}
+
 	switch m := m.(type) {
 	case *message.CommandMsg:
 		cmd := *m
@@ -150,6 +181,7 @@ func (r *Room) Join(u *message.User) (*Member, error) {
 	if err != nil {
 		return nil, err
 	}
+	// TODO: Remove user ID from sets, probably referring to a prior user.
 	r.History(u)
 	s := fmt.Sprintf("%s joined. (Connected: %d)", u.Name(), r.Members.Len())
 	r.Send(message.NewAnnounceMsg(s))
diff --git a/chat/room_test.go b/chat/room_test.go
index 44c8f0c..2f78961 100644
--- a/chat/room_test.go
+++ b/chat/room_test.go
@@ -158,6 +158,94 @@ func TestIgnore(t *testing.T) {
 	expectOutput(t, buffer, ignored.user.Name()+": hello again!"+message.Newline)
 }
 
+func TestMute(t *testing.T) {
+	var buffer []byte
+
+	ch := NewRoom()
+	go ch.Serve()
+	defer ch.Close()
+
+	// Create 3 users, join the room and clear their screen buffers
+	users := make([]ScreenedUser, 3)
+	members := make([]*Member, 3)
+	for i := 0; i < 3; i++ {
+		screen := &MockScreen{}
+		user := message.NewUserScreen(message.SimpleID(fmt.Sprintf("user%d", i)), screen)
+		users[i] = ScreenedUser{
+			user:   user,
+			screen: screen,
+		}
+
+		member, err := ch.Join(user)
+		if err != nil {
+			t.Fatal(err)
+		}
+		members[i] = member
+	}
+
+	for _, u := range users {
+		for i := 0; i < 3; i++ {
+			u.user.HandleMsg(u.user.ConsumeOne())
+			u.screen.Read(&buffer)
+		}
+	}
+
+	// Use some handy variable names for distinguish between roles
+	muter := users[0]
+	muted := users[1]
+	other := users[2]
+
+	members[0].IsOp = true
+
+	// test muting unexisting user
+	if err := sendCommand("/mute test", muter, ch, &buffer); err != nil {
+		t.Fatal(err)
+	}
+	expectOutput(t, buffer, "-> Err: user not found"+message.Newline)
+
+	// test muting by non-op
+	if err := sendCommand("/mute "+muted.user.Name(), other, ch, &buffer); err != nil {
+		t.Fatal(err)
+	}
+	expectOutput(t, buffer, "-> Err: must be op"+message.Newline)
+
+	// test muting existing user
+	if err := sendCommand("/mute "+muted.user.Name(), muter, ch, &buffer); err != nil {
+		t.Fatal(err)
+	}
+	expectOutput(t, buffer, "-> Muted: "+muted.user.Name()+message.Newline)
+
+	if got, want := members[1].IsMuted(), true; got != want {
+		t.Error("muted user failed to set mute flag")
+	}
+
+	// when an emote is sent by a muted user, it should not be displayed for anyone
+	ch.HandleMsg(message.NewPublicMsg("hello!", muted.user))
+	ch.HandleMsg(message.NewEmoteMsg("is crying", muted.user))
+
+	if muter.user.HasMessages() {
+		muter.user.HandleMsg(muter.user.ConsumeOne())
+		muter.screen.Read(&buffer)
+		t.Errorf("muter should not have messages: %s", buffer)
+	}
+	if other.user.HasMessages() {
+		other.user.HandleMsg(other.user.ConsumeOne())
+		other.screen.Read(&buffer)
+		t.Errorf("other should not have messages: %s", buffer)
+	}
+
+	// test unmuting
+	if err := sendCommand("/mute "+muted.user.Name(), muter, ch, &buffer); err != nil {
+		t.Fatal(err)
+	}
+	expectOutput(t, buffer, "-> Unmuted: "+muted.user.Name()+message.Newline)
+
+	ch.HandleMsg(message.NewPublicMsg("hello again!", muted.user))
+	other.user.HandleMsg(other.user.ConsumeOne())
+	other.screen.Read(&buffer)
+	expectOutput(t, buffer, muted.user.Name()+": hello again!"+message.Newline)
+}
+
 func expectOutput(t *testing.T, buffer []byte, expected string) {
 	t.Helper()