I have a Labrador who keeps eating poop.

Here's a hub that I have published that deals with this exact issue.

http://hubpages.com/hub/Coprophagia

This is a very nasty habit indeed. Here is a hub that I have done on this topic which provides the tips that I used to get my dog to stop this disgusting act.

http://hubpages.com/hub/How-to-Stop-My-Dog-From-Ea

IT is a common problem among dogs - not just Labradors. Many Retrievers do it as well. As the first comment suggests there are things on the market you can add to meals to make it less tasty to your dog. What did your vet suggest?

My Labs do the same exact thing. It has only gotten worse as they have aged. Pills from the Vet did nothing.

Now we clean the yard immediately after they goto the bathroom, and sometimes we must place a muzzle type face mask on them. (I try not to use it though!)

Normally when a dog eats its own poop, it is lacking something in its diet. Try changing the food that you feed it and good luck.

Maybe it's a monkey see monkey do scenario. If so, quit eating poop.

This may sound dumb, but if he eats only cat poop, you can move the litter box to a place out of his reach. The basement is where we keep ours. Also, a covered litter box usually will stop that from happening. You can pick one up at a pet store or wal-mart for around twenty dollars.