Personally, I don't like using the collar until the pup is aleast six months old. I use it as a reinforment tool, ie. the dog gotta know why he's being corrected which ofcourse means he must know the command he is disobeying. I put it on my dog at nine months but circumstances forced it, if not I would have held off til a year.

It all depends upon the training program your following and the maturity of the dog. Used unwisely, and you can create problems.