[cgrohman]

This is a very simple version. The only time you win is when you improve and he does not improve.

Lets assume a standard eight handed game that gets head up on 3rd. You know all 6 of your cards, the 4 upcards of your opponent, and the 6 upcards of people who folded on third. That means there are 36 cards left. You need 4 out of those 36, so your chances of hitting are 1/9.

Likewise, you need your opponent to miss. He will miss his 4 full-house outs, 8/9 times (I got lazy and didnt subtract the extra card off).

So you will win (1/9)*(8/9) of the time or 8/81 . . . so approximately 10 percent. Pot better be laying your good odds.