http://www.cdc.gov/hiv/topics/msm/protection.htm
Centers for Disease Control and Prevention, U.S. Department of Health and Human Services
The term men who have sex with men (MSM) refers to all men who have sex with other men, regardless of how they identify themselves (gay, bisexual, or heterosexual). AIDS has been diagnosed for more than half a million MSM. Learn what you can do to protect yourself from getting HIV or passing it to someone else.