Little is known about interventions in office practices aimed toward reducing behaviors that put adolescents at risk for human immunodeficiency virus (HIV) acquisition. We therefore targeted a pilot study of HIV education and counseling to high-risk adolescents. Ninety adolescent patients (mean age, 17.6 +/- 2.0 years) were interviewed in a hospital-based adolescent clinic by two physicians and randomized to two groups: 1) a standard care group that was interviewed about high-risk behaviors at 0 and 2 months; and 2) an intervention group that was similarly interviewed but was also given a detailed discussion about HIV risks and prevention. At follow-up (mean, 2.6 +/- 0.8 months), 25% of patients reported less sexual activity (standard care, 32%; intervention, 18%) toward a trend. The reduction in mean number of partners per month was 0.4 +/- 0.9, (p = 0.0001). Fifty-four percent of the patients reported that they used condoms more often than previously with no significant difference between the two groups. Use of condoms ("always use") increased in both groups significantly (p = 0.03 standard care, p = 0.02 intervention). Use of condoms at last intercourse increased in the intervention group (37% to 42%, p = 0.03). In the interval, there were no significant differences between the groups in the number of newly diagnosed sexually transmitted diseases or in the number of patients seeking HIV testing. The number of patients stating that they shared needles decreased from 3 to 0. Both the intervention and standard care groups reported a reduction in high-risk behaviors that was temporally related to the discussion of this subject in the clinic.(ABSTRACT TRUNCATED AT 250 WORDS)