In a multicenter study, a long-term analysis was made of the efficacy, safety, and tolerability of subcutaneous (s.c.) sumatriptan in the acute treatment of migraine attacks over a period of up to 18 months. A total of 2263 patients took part in the study, all able to perform their own acute treatment of migraine attacks at home by s.c. administration of 6 mg of sumatriptan. A headache diary was used by each patient to record the various migraine parameters before the injection and 1 h and 2 h after it. A total of 43,691 attacks were treated and analyzed during the study period from October 1991 to June 1993. Therapy was successful in 89.5% of attacks. Freedom from headache was achieved in 71.0% of cases. In 22.7% of the attacks a second injection was administered on recurrence of the headache; 82.9% of the patients achieved an intraindividual therapy success rate ranging from over 80% to 100%. In the course of treatment there was no change in either the therapy success rate or in the frequency of attacks. Some 4.9% of the patients withdrew from the study because of insufficient efficacy or adverse events. A total of 44.5% of patients reported adverse events, and these were rated serious in the case of 1.7%. S.c. administration of sumatriptan for acute migraine therapy is an effective treatment method, with reliable action, that can be used with good tolerability provided the contraindications are taken into account.