Human papillomavirus or HPV is the most common sexually transmitted infection in the United States. The virus commonly causes genital and anal warts, and less commonly causes anal, penile and oral (mouth and throat) cancers.
Nearly 100% of sexually active men who have sex with men have been infected with HPV at some point in their lives, even if they've never had an visible genital wart.
Most men's immune systems can knock out the HPV virus eventually and they never have any long term consequences from their HPV infection.
Unfortunately, in a small number of these cases, the HPV virus can go on to cause cancer to develop in the anus, on the penis or in the mouth/throat. HIV positive guys are at the highest risk for HPV related cancer, but HIV negative guys can get it too.
The good news is that there is now a vaccine available to men 26 and younger (down to age 9), that can prevent most cases of HPV related cancer. The vaccine is most effective if you get it before you start to have sex, but is still worth getting later. Ask your doctor about getting the HPV vaccine if you are 26 or younger.