To describe clinically important differences in the characteristics of subjects using three distinct HIV counseling and testing settings: scheduled confidential, scheduled anonymous, and confidential walk-in. An HIV risk-assessment questionnaire was given to individuals prior to receiving HIV-antibody testing and counseling. Demographic and behavioral data was analyzed for each of the three counseling and testing settings. Walk-in clinic subjects reported fewer high-risk sexual activities and other risk behaviors than subjects from the other two testing settings. They also included more individuals who were health-care workers and victims of sexual assault. The three distinct HIV counseling and testing settings each attracted populations with varying degrees of potential for HIV transmission. The results emphasize the importance of maintaining multiple approaches to HIV counseling and testing in order to reach increasingly diverse at-risk populations.