hearing back from interview

Is it wrong to contact a company if you havent heard back from an interview. Does it give the wrong impression or maybe the impression that you are keen. Its a few weeks since the interview? Was told it would be a few weeks but am beginning to loose patience now!!

Thanks

My own honest opinion, I'd contact them and rather than asking specifically about your interview I'd approach it from the view point of generally asking if they have come to any conclusions about xyz job that they interviewed for.

thanks for reply - am going to contact them tomorrow.
Regards