I had a biter and ended up giving the parents a warning. After that I would constantly have this baby (18 months) in my view. I would put him in time out and now he hasn't bitten in weeks. The parents were very supportive and were working with him at home as well. They stopped doing anything with him that would be seen by him as aggressive such as play fighting. I also started to realize that the girl that he was biting tended to tattle on him and take things away from him so I imagine that he was getting frustrated because he couldn't explain his side of the story.