Two hundred and thirty migraineurs diagnosed by their general practitioners in accordance with their usual practice were included. The patients treated two migraine attacks at home by subcutaneous injection of sumatriptan or placebo and the alternative medication for the second attack (cross-over). When sumatriptan was compared to placebo, significantly more of the 209 evaluable patients reported headache relief at one hour (56% v 8%, p < 0.001) and two hours (62% v 15%, p < 0.001) after the first injection. Resolution of nausea, photophobia and phonophobia was significantly more common in patients on sumatriptan than on placebo (p < 0.001 for all comparisons). The adverse events were usually transient and of mild or moderate severity, although, three patients withdrew due to adverse events. Ninety-five percent of patients evaluated by a neurological research fellow met the International Headache Society's criteria for migraine. In general practice, sumatriptan taken subcutaneously using an autoinjector at home was an effective and well tolerated acute treatment for migraine.