Replication filter works for initialization but is not working after initialization for transaction replication SQL2008R2?

Where can I start to look for why this is happening?

Immediately after I reinitialize the subscription data is correct, the filter worked. But as the day goes on replicated data does not have the filter applied. Too much data is being replicated. Where do I start to look for why this is happening? This SQL2008R2 RTM.

Tom G.