Well into the third decade of the human immunodeficiency virus (HIV) epidemic, rates of HIV infection remain high, especially among minority populations. Of newly diagnosed HIV infections in the United States during 2003, CDC estimated that approximately 63% were among men who were infected through sexual contact with other men, 50% were among blacks, 32% were among whites, and 16% were among Hispanics. Studies of HIV infection among young men who have sex with men (MSM) in the mid to late 1990s revealed high rates of HIV prevalence, incidence, and unrecognized infection, particularly among young black MSM. To reassess those findings and previous HIV testing behaviors among MSM, CDC analyzed data from five of 17 cities participating in the National HIV Behavioral Surveillance (NHBS) system. This report summarizes preliminary findings from the HIV-testing component of NHBS, which indicated that, of MSM surveyed, 25% were infected with HIV, and 48% of those infected were unaware of their infection. To decrease HIV transmission, MSM should be encouraged to receive an HIV test at least annually, and prevention programs should improve means of reaching persons unaware of their HIV status, especially those in populations disproportionately at risk.