The aim of the open prospective study was to investigate the efficacy, safety and tolerability of subcutaneous sumatriptan in acute migraine treatment. Patient self-treatment was monitored over a time period of 6-18 months with 6 mg of sumatriptan administered subcutaneously by an autoinjector. In total, 2,263 patients participated in the study. Headache intensity was documented by the patient in a headache diary before and 1 and 2 h after application. During the study period from October 1991 to June 1993, 43,691 migraine attacks were investigated. Treatment with sumatriptan was efficient in 89.5% of the attacks. Headache relief was achieved in 71%. Headache reoccurred in 22.7% of the attacks, and therefore a second injection was administered. An intraindividual treatment efficacy of 80-100% was achieved in 82.9% of the patients. During long-term treatment the ratio of effective treatment and headache frequency was constant; 4.9% of the patients withdrew from the study because of adverse events and because they felt the treatment was not effective. A total of 44.5% of the patients reported adverse events that were serious in 1.7%. Subcutaneous self-treatment with sumatriptan in the acute treatment of migraine is effective and well tolerated by the patients.