My Cairne Terrier is 3 yrs old and he urinates all over the house, I've tried watching him but I never seem to be able to catch him doing it, it is really annoying now, can someone come up with the correct solution.

When he pee's make sure you clean it up REALLY good, because he will keep smelling his urine and keep peeing there. A good thing to clean it with is vinager (Or bleach but if it is on carpet I wouldn't risk it). Try tying him to you with a longish lead, this way he won't be able to pee. How often do you let him out? Try letting him out more. When deos he eat/drink? Try limiting his feeding and drinking. Feed and water him on a schedule this way he'll pee and poop on a schedule.

Denny, how long have you had this dog? Was he housebroken before and is suddenly beginning to pee in the house or is it now finally getting on your nerves after 3 years? Is he neutered?

Need more background info so I know what detailed advice to give.

In the meantime, as long as you let him roam freely around the house, he is going to pee when he feels like it. Take Emily's suggestion of tying him to you on a long lead so you can get him outside as soon as you see him signaling he is ready to pee. When you don't have the time to watch him, then crate him in between your walks with him.