diff --git a/irc/channel.go b/irc/channel.go
index 362178ad..767509d2 100644
--- a/irc/channel.go
+++ b/irc/channel.go
@@ -18,6 +18,13 @@ type Channel struct {
 
 type ChannelSet map[*Channel]bool
 
+func (channels ChannelSet) First() *Channel {
+	for channel := range channels {
+		return channel
+	}
+	return nil
+}
+
 type ChannelCommand interface {
 	Command
 	HandleChannel(channel *Channel)
diff --git a/irc/commands.go b/irc/commands.go
index 11a9059e..7f4e98b2 100644
--- a/irc/commands.go
+++ b/irc/commands.go
@@ -35,6 +35,7 @@ var (
 		"QUIT":    NewQuitCommand,
 		"TOPIC":   NewTopicCommand,
 		"USER":    NewUserMsgCommand,
+		"WHO":     NewWhoCommand,
 		"WHOIS":   NewWhoisCommand,
 	}
 )
@@ -485,7 +486,7 @@ type WhoisCommand struct {
 	masks  []string
 }
 
-// [ <target> ] <mask> *( "," <mask> )
+// WHOIS [ <target> ] <mask> *( "," <mask> )
 func NewWhoisCommand(args []string) (EditableCommand, error) {
 	if len(args) < 1 {
 		return nil, NotEnoughArgsError
@@ -506,3 +507,24 @@ func NewWhoisCommand(args []string) (EditableCommand, error) {
 		masks:  strings.Split(masks, ","),
 	}, nil
 }
+
+type WhoCommand struct {
+	BaseCommand
+	mask         string
+	operatorOnly bool
+}
+
+// WHO [ <mask> [ "o" ] ]
+func NewWhoCommand(args []string) (EditableCommand, error) {
+	cmd := &WhoCommand{}
+
+	if len(args) > 0 {
+		cmd.mask = args[0]
+	}
+
+	if (len(args) > 1) && (args[1] == "o") {
+		cmd.operatorOnly = true
+	}
+
+	return cmd, nil
+}
diff --git a/irc/reply.go b/irc/reply.go
index f17da108..a27e20ab 100644
--- a/irc/reply.go
+++ b/irc/reply.go
@@ -239,6 +239,19 @@ func RplChannelModeIs(server *Server, channel *Channel) Reply {
 		channel.name, channel.ModeString())
 }
 
+// <channel> <user> <host> <server> <nick> ( "H" / "G" ) ["*"] [ ( "@" / "+" ) ]
+// :<hopcount> <real name>
+func RplWhoReply(server *Server, channel *Channel, client *Client) Reply {
+	return NewNumericReply(server, RPL_WHOREPLY, "%s %s %s %s %s H :0 %s",
+		channel.name, client.username, client.hostname, server.name, client.nick,
+		client.realname)
+}
+
+// <name> :End of WHO list
+func RplEndOfWho(server *Server, name string) Reply {
+	return NewNumericReply(server, RPL_ENDOFWHO, "%s :End of WHO list", name)
+}
+
 // errors (also numeric)
 
 func ErrAlreadyRegistered(source Identifier) Reply {
diff --git a/irc/server.go b/irc/server.go
index 21cdadff..2137baf5 100644
--- a/irc/server.go
+++ b/irc/server.go
@@ -310,3 +310,32 @@ func (msg *ChannelModeCommand) HandleServer(server *Server) {
 
 	client.replies <- RplChannelModeIs(server, channel)
 }
+
+func whoChannel(client *Client, server *Server, channel *Channel) {
+	for member := range channel.members {
+		client.replies <- RplWhoReply(server, channel, member)
+	}
+}
+
+func (msg *WhoCommand) HandleServer(server *Server) {
+	client := msg.Client()
+	// TODO implement wildcard matching
+
+	if msg.mask == "" {
+		for _, channel := range server.channels {
+			whoChannel(client, server, channel)
+		}
+	} else if IsChannel(msg.mask) {
+		channel := server.channels[msg.mask]
+		if channel != nil {
+			whoChannel(client, server, channel)
+		}
+	} else {
+		mclient := server.clients[msg.mask]
+		if mclient != nil {
+			client.replies <- RplWhoReply(server, mclient.channels.First(), mclient)
+		}
+	}
+
+	client.replies <- RplEndOfWho(server, msg.mask)
+}