Filtering Joined/Left text in Messages

Hi,

I use a fairly busy Jabber server with group rooms and am inundated with joined/left messages:

xxx@myjabber.com has joined this chat.
xxx@myjabber.com has left this chat.​

Can these be filtered? often after being idle for hours i'll have to scroll through pages of this to see previous content or messages posted.

Cheers,

Atomic.