diff --git a/degesch.c b/degesch.c
index eca8a89..20e1ff7 100644
--- a/degesch.c
+++ b/degesch.c
@@ -1206,8 +1206,33 @@ init_buffers (struct app_context *ctx)
 	LIST_APPEND_WITH_TAIL (ctx->buffers, ctx->buffers_tail, server);
 }
 
+// --- Users, channels ---------------------------------------------------------
+
 // --- Supporting code ---------------------------------------------------------
 
+static char *
+irc_cut_nickname (const char *prefix)
+{
+	return xstrndup (prefix, strcspn (prefix, "!@"));
+}
+
+static bool
+irc_is_this_us (struct app_context *ctx, const char *prefix)
+{
+	char *nick = irc_cut_nickname (prefix);
+	bool result = !irc_strcmp (nick, ctx->irc_nickname);
+	free (nick);
+	return result;
+}
+
+static bool
+irc_is_channel (struct app_context *ctx, const char *ident)
+{
+	(void) ctx;  // TODO: parse prefixes from server features
+
+	return *ident && !!strchr ("#&+!", *ident);
+}
+
 static void
 irc_shutdown (struct app_context *ctx)
 {
@@ -1712,8 +1737,69 @@ irc_to_utf8 (struct app_context *ctx, const char *text)
 static void
 irc_handle_join (struct app_context *ctx, const struct irc_message *msg)
 {
-	// TODO: if the user is us, create a new buffer and activate it.
-	// TODO: log a message
+	if (!msg->prefix || msg->params.len < 1)
+		return;
+
+	const char *target = msg->params.vector[0];
+	if (!irc_is_channel (ctx, target))
+		return;
+
+	struct channel *channel = str_map_find (&ctx->irc_channels, target);
+	struct buffer *buffer = str_map_find (&ctx->irc_buffer_map, target);
+	hard_assert ((channel && buffer) ||
+		(channel && !buffer) || (!channel && !buffer));
+
+	// We've joined a new channel
+	if (!channel && irc_is_this_us (ctx, msg->prefix))
+	{
+		channel = channel_new ();
+		channel->name = xstrdup (target);
+		channel->mode = xstrdup ("");
+		channel->topic = NULL;
+		str_map_set (&ctx->irc_channels, channel->name, channel);
+
+		buffer = buffer_new ();
+		buffer->type = BUFFER_CHANNEL;
+		buffer->name = xstrdup (target);
+		buffer->channel = channel_ref (channel);
+		LIST_APPEND_WITH_TAIL (ctx->buffers, ctx->buffers_tail, buffer);
+		str_map_set (&ctx->irc_buffer_map, channel->name, buffer);
+
+		buffer_activate (ctx, buffer);
+	}
+
+	// This is weird, ignoring
+	if (!channel)
+		return;
+
+	// Get or make a user object
+	char *nickname = irc_cut_nickname (msg->prefix);
+	struct user *user = str_map_find (&ctx->irc_users, nickname);
+	if (!user)
+	{
+		user = user_new ();
+		user->nickname = nickname;
+		str_map_set (&ctx->irc_users, user->nickname, user);
+	}
+	else
+		free (nickname);
+
+	// Link the user with the channel
+	struct user_channel *user_channel = user_channel_new ();
+	user_channel->channel = channel_ref (channel);
+	LIST_PREPEND (user->channels, user_channel);
+
+	struct channel_user *channel_user = channel_user_new ();
+	channel_user->user = user_ref (user);
+	channel_user->modes = xstrdup ("");
+	LIST_PREPEND (channel->users, channel_user);
+
+	// Finally log the message
+	if (buffer)
+	{
+		buffer_send (ctx, buffer, BUFFER_LINE_JOIN, 0,
+			msg->prefix, NULL, "%s", target);
+	}
 }
 
 static void