The outcomes of sumatriptan use at a health maintenance organization (HMO) were studied. The study was conducted during one year beginning immediately after sumatriptan was added to the formulary of a large group-model HMO. Subjects were included on the basis of drug-use evaluation criteria, a positive response to the first dose of sumatriptan (administered at the HMO by a nurse), and ability to participate in a telephone survey. Responders to the first dose were eligible to receive up to six doses of sumatriptan for home use. The telephone survey was designed to assess sumatriptan's effects on migraine headache and to capture data on quality of life, perceived problems with sumatriptan, and patient satisfaction. Patients who received sumatriptan between April and September 1993 were interviewed in late September 1993; patients who received sumatriptan between September and April 1994 were interviewed in late April 1994. Of 180 patients surveyed, 160 (89%) had evaluable responses. Migraine headache improved in two thirds of the patients. Sumatriptan was more effective than previously used agents in three fourths. The mean number of migraine headaches per patient per month decreased from 7.4 to 4.2. Quality-of-life indicators, such as time spent with friends, improved in three fourths. Eighty-three percent reported missing fewer days from work. Ninety percent said they would continue to take the drug, despite a 44% incidence of drug-related problems. There were no unexpected problems. A retrospective review showed that utilization of the HMO's resources was reduced with sumatriptan. Placing sumatriptan on an HMO's formulary led to favorable effects on the frequency and severity of migraine headache, patient quality-of-life indicators and productivity, and resource utilization by the organization.