Aim: The study tried to investigate the efficacy, adverse events and possible risk factors of sumatriptan in daily clinical practice. Patients arn Methods: 72 outdoor patients, who had treated their headaches at least once with sumatriptan, partly prescribed to them by outdoor physicians, were asked about their experiences with the drug. According to the criteria of the International Headache Society (1988) 55 patients were suffering from migraine, 11 from cluster headache and 6 from tension-type headache. Results: Migraine and cluster patients rated the drug as effective as described in literature. Adverse events were reported by 69% of the patients, which was more frequent than in most clinic studies described. Adverse events were usually not serious and transient. They were reported significantly more often by migraine patients than by patients with cluster headache and might not all be con-elated to the therapy of sumatriptan. Conclusion: Sumatriptan has shown to be effective in the treatment of an acute migraine and cluster-headache. The risk as to severe adverse events, especially cardial adverse events, exists if contraindications for sumatriptan are not considered. Sumatriptan should therefore only be prescribed to carefully diagnosed migraine and cluster headache patients. It should, however, not be given to patients suffering from drug abuse, because they might just change over to sumatriptan.