New medications for HIV reduce mortality and morbidity but require strict adherence. Thus, physicians treating HIV-positive patients must weigh both disease severity and likelihood of adherence when deciding whether to start patients on treatment. A national sample of 495 physicians surveyed via mail responded to clinical scenarios depicting HIV-positive patients and indicated whether they would start patients on medication (response rate = 53%). Scenarios varied on the patient characteristics of gender, disease severity, ethnicity, and risk group. Physicians predicted that patients with less severe disease, former injection drug users, and African American men would be less likely to adhere. Perceived adherence and disease severity influenced treatment decisions. Results are discussed in the context of attitudes about minority groups and injection drug users, which may influence adherence judgments in practice settings. Psychological research to identify better methods of predicting medication adherence may serve to inform medical decision making.