Effective HIV prevention interventions with HIV-positive persons are paramount to stemming the rate of new infections. This paper describes an HIV-clinic-based demonstration project aimed at decreasing patient HIV-transmission risk behaviors and sexually transmitted infections. Systematic, computer-assisted assessment of patient risk aided primary care providers in delivering prevention messages. Patients at greater risk were referred to an HIV Prevention Specialist for behavioral counseling. Patients completed a computerized behavioral staging assessment to self-identify risk behaviors and readiness to change behaviors and counseling messages were individually tailored based on computer assessment. Challenges to project implementation: primary care provider buy-in, patient privacy concerns during risk assessment, and low participation in behavioral counseling. Forty-six percent of persons completing a risk assessment (2,124) were at risk for HIV transmission. Of 121 patients who scheduled counseling appointments, 42% completed at least one session. Despite challenges, successful implementation of a clinic-based prevention intervention is feasible, particularly with attention to patient and provider concerns.