Twenty years after the first report on human immunodeficiency virus (HIV) infection in the United States, studies of sexually transmitted diseases (STDs) and sexual behaviors suggest a resurgent HIV epidemic among men who have sex with men (MSM). However, few recent studies have measured HIV incidence in this population. To determine HIV incidence among young MSM, CDC analyzed data from the Young Men's Survey (YMS), a study that found a high prevalence of HIV and associated risks among MSM aged 15-22 years sampled in seven U.S. cities. This report confirms high HIV incidence among these young men.