To explore recent patterns in the HIV epidemic in young gay and bisexual men, we analyzed national AIDS surveillance data for men who have sex with men (MSM) 13 to 25 years of age. Estimates of annual AIDS incidence were calculated by adjusting the surveillance data for reporting delays, unreported HIV risks, and the 1993 change in the AIDS case definition. Between 1990 and 1995, estimated AIDS incidence in young MSM declined 29%, from 1400 to 1000 cases; however, trends in incidence varied greatly by race/ethnicity. Annual AIDS incidence decreased 50% in whites during this period (from 720 to 360), but fell just 2% in blacks (from 430 to 420) and rose 5% in Hispanics (from 220 to 230). Trends in incidence also differed by metropolitan statistical area (MSA) size. Between 1990 and 1995, AIDS incidence declined 37% in MSAs with populations of 2,500,000 people or more and 28% in MSAs with 1,000,000 to 2,499,999 people, but incidence decreased only 15% in MSAs with 500,000 to 999,999 people, and 13% in MSAs with 50,000 to 499,999. Incidence in nonmetropolitan (i.e., rural) areas was unchanged. Young black and Hispanic MSM now account for most young MSM with AIDS, and incidence in young MSM in small MSAs and rural areas has been relatively constant. Trends in AIDS incidence indicate that levels of HIV infection have remained persistently high in certain populations of young MSM, underscoring the immense need for HIV prevention programs targeted specifically toward these young men.