In addition to what Sanka said, we really need more information. How old is the dog? Is this a new behavior or ongoing? How often does he go out and, especially as Sanka pointed out...do you go out with him and make sure he has peed????
Many people put the dog outside for an hour or so, then let it in and expect it has gone. In many cases the dog is outside playing or exploring or lying in the warm sun and doesn't go, getting up and coming inside stimulates him and he does it inside.
Speaking of, how well are you cleaning the area when he has gone?? You need to use an enzyme cleaner as HE can still smell it, even if you can't.
Finally, is he peeing inside OR is he marking??? Makes a big difference, especially in a male dog. If it's marking, neutering can often help but won't be a cure-all as you will still need to do some training with him.

Toto, CD, RN, CGC answered on 11/6/11. Helpful? / 0