As part of the American Psychiatric Association's national Practice Research Network (PRN), this pilot study tested a data collection instrument designed to systematically characterize the sociodemographic and diagnostic characteristics of psychiatric patients and the specific treatments they received, including specific psychopharmacologic medications, Ninety-five percent of the PRN members (148 of 156 psychiatrists), who practice in a broad range of settings, completed a 21-page data collection instrument that generated detailed diagnostic, clinical, and treatment data on 290 psychiatric patients, Mood disorders constituted the most common principal DSM-IV diagnostic category, affecting 53 percent of the patients in this pilot study, The majority of patients had significant psychiatric and general medical cooccurring conditions; 20 percent of the patients had at least three DSM-IV Axis I mental disorders, Ninety percent of all patients in the sample received at least one psychopharmacologic medication, with each patient, on average, receiving 1.8 (SD=1.2). After adjustment for patients' diagnostic and clinical characteristics, the mean number of medications prescribed per patient in this pilot study sample did not vary by health plan type or payment source. However, the combinations of treatments provided by psychiatrists (i.e., psychotherapy and medications) did vary by health plan type and payment source.