The majority of persons living with human immunodeficiency virus (HIV) in the United States are men who have sex with men (MSM). High-risk sexual behavior by HIV-positive MSM exposes sex partners to HIV. The risk for transmitting HIV from an infected partner to an uninfected partner through unprotected insertive anal intercourse (UIAI) is greater than the risk for transmission through receptive anal intercourse or oral sex. Differences in sexual risk behavior might be associated with the perceived HIV serostatus of the partner (i.e., HIV positive, HIV negative, or unknown serostatus), as well as with the sex partner type (i.e., steady or nonsteady). During May 2000-December 2002, HIV-positive MSM were interviewed in a behavioral surveillance survey at surveillance sites in 16 states. This report describes insertive anal intercourse practices reported by these MSM; findings indicated that a large percentage of HIV-positive MSM were sexually abstinent, practiced safer sexual behavior by having protected insertive anal intercourse, or had UIAI with an HIV-positive partner. However, a small percentage of HIV-positive MSM reported UIAI with partners who were HIV negative or whose serostatus was unknown; for this group, more intensive and comprehensive HIV-prevention efforts are needed to eliminate this risk behavior.