PURPOSE To determine if a brief intervention that provides information about AIDS clinical trials to HIV-infected patients at the initiation of primary care increases the participation of women, persons of color, and injection drug users (IDUs) in clinical trials. METHOD 196 outpatients beginning HIV primary care at a municipal hospital were followed from September 1994 to April 1996. During the intake assessment, each patient met briefly with a research assistant who described the purpose, role, and availability of clinical trials. Contacts for further information about trials were given to patients who expressed interest. At the end of the 20-month period, enrollment rates of all patients, including women, persons of color, and IDUs, into clinical trials were compared with previously published enrollment rates of patients at the same hospital but prior to the development of this brief intervention. RESULTS The characteristics of the 196 HIV-infected patients were: 27% women; 47% IDUs; 14% gay/bisexual men; and 76% persons of color. Overall enrollment in AIDS clinical trials was 14.8% during the 20-month follow-up period. There was no significant difference in participation rates between males and females (p =.20), whites and persons of color (p =.71), and IDUs compared with non-IDUs (p =.90), whereas previously published data had shown significantly higher enrollment rates among males, whites, and non-IDUs. CONCLUSION Providing all HIV-infected patients with information about the meaning, role, and availability of AIDS clinical trials at the initiation of HIV primary care reduces differences in participation rates by gender, race, and history of drug use.