diff --git a/README b/README
index 0a11809..f3a0ec0 100644
--- a/README
+++ b/README
@@ -4,7 +4,7 @@
 DESCRIPTION
 
 goircd is very simple IRC server, written on Go.
-It is heavily inspired by miniircd daemon written on Python.
+It was heavily inspired by miniircd daemon written on Python.
 GoVPN is free software: see the file COPYING for copying conditions.
 It does not aim to replace full featured mass scalable IRC networks:
 
@@ -35,7 +35,7 @@ SUPPORTED IRC COMMANDS
 
 * PASS/NICK/USER during registration workflow
 * PING/PONGs
-* NOTICE/PRIVMSG
+* NOTICE/PRIVMSG, ISON
 * AWAY, MOTD, LUSERS, WHO, WHOIS, VERSION, QUIT
 * LIST, JOIN, TOPIC, +k/-k channel MODE
 
diff --git a/daemon.go b/daemon.go
index b795a0c..1af9712 100644
--- a/daemon.go
+++ b/daemon.go
@@ -486,6 +486,22 @@ func Processor(events chan ClientEvent, finished chan struct{}) {
 				cols := strings.Split(cols[1], " ")
 				nicknames := strings.Split(cols[len(cols)-1], ",")
 				SendWhois(client, nicknames)
+			case "ISON":
+				if len(cols) == 1 || len(cols[1]) < 1 {
+					client.ReplyNotEnoughParameters("ISON")
+					continue
+				}
+				nicksKnown := make(map[string]struct{})
+				for c := range clients {
+					nicksKnown[*c.nickname] = struct{}{}
+				}
+				var nicksExists []string
+				for _, nickname := range strings.Split(cols[1], " ") {
+					if _, exists := nicksKnown[nickname]; exists {
+						nicksExists = append(nicksExists, nickname)
+					}
+				}
+				client.ReplyNicknamed("303", strings.Join(nicksExists, " "))
 			case "VERSION":
 				var debug string
 				if *verbose {