Concerns are often raised regarding the credibility of patients' report of pain and this concern is heightened among individuals with AIDS, where many patients have a history of injection drug use. This study compared the pain experience, adequacy of pain management and psychological well-being among patients with AIDS who reported a history of injection drug use (IDU) as their HIV transmission risk factor and patients with other HIV transmission risk factors. Five hundred and sixteen ambulatory AIDS patients participating in a quality of life study completed a series of self-report instruments including the Brief Pain Inventory, the Beck Depression Inventory, the Brief Symptom Inventory, the Functional Living Inventory and the Social Support Questionnaire. Results demonstrated that IDU and non-IDU subjects did not differ significantly in their report of pain prevalence, pain intensity or pain-related functional interference. However, IDU patients were significantly more likely to receive inadequate analgesic medications, reported lower levels of pain relief and a greater degree of psychological distress. There was also no difference in report of pain intensity, pain relief or functional interference among patients who acknowledged continued drug use, those who denied any recent drug use and patients participating in a methadone maintenance program. These data support the validity of AIDS patients' report of pain, at least in research settings, and suggest that undertreatment of pain is not restricted to patients who actively abuse drugs.