Information about the characteristics of persons whose HIV diagnosis was made soon after infection contributes to a better understanding of the HIV epidemic and to appropriate targeting of care and prevention efforts. In 10 US cities from 1997 through 2001, specimens from consenting persons for whom a diagnosis of HIV was made within the past 12 months in were tested using the serologic testing algorithm for recent HIV seroconversion. The characteristics of those whose HIV diagnosis occurred within 170 days (on average) from seroconversion were identified. For 191 (20%) of the 964 participants, an HIV diagnosis was made during the period of recent infection. These diagnoses of recent infection were made more frequently among men (21.7%), whites (29.3%), men who have sex with men (25.5%), persons with a known HIV-infected partner (24.9%), and persons with a diagnosis of gonorrhea made in the 12 months before interview (27.0%). Recent infection was diagnosed less frequently among African Americans (15.5%), Latinos (15.5), and heterosexual men (14.7%) and women (14.4%). To increase early diagnosis of HIV, HIV testing should be more routinely offered to persons with a recent history of sexually transmitted diseases and to African Americans and Latinos in a variety of settings.