Data from the National Prescription Audit and the National Disease and Therapeutic Index were used to assess trends in outpatient prescriptions for antipsychotic drugs in the United States from 1976 to 1985. Retail pharmacies dispensed 21 million prescriptions for antipsychotic drugs in 1976 and 19 million in 1985. The three leading antipsychotic drugs-thioridazine, haloperidol, and chlorpromazine-constituted 66% to 69% of antipsychotic prescriptions and, along with trifluoperazine, thiothixene, and fluphenazine, accounted for 90% to 91% of all antipsychotic prescriptions throughout the period studied. Thioridazine was the leading medication, with a consistent third of the market share, while the market share for chlorpromazine decreased from 1976 to 1985 and that for haloperidol increased for the same years. Data also indicate that haloperidol is the antipsychotic drug used most frequently in office-based, private medical practice for patients 60 years of age and older, a declining proportion of women are treated with antipsychotic medications, and use of antipsychotic drugs as monotherapy for the primary diagnosis is increasing. We also obtained data on diagnoses associated with antipsychotic drug use.