The efficacy and safety of oral sumatriptan as a 100-mg dispersible tablet was compared with oral Cafergot (2 mg ergotamine tartrate, 200 mg caffeine) in a multicentre, randomized, double-blind, double-dummy, parallel-group trial. In the trial, 580 patients were treated from 47 investigating centres in nine European countries. Sumatriptan was significantly more effective than Cafergot at reducing the intensity of headache from severe or moderate to mild or none; 66% (145/220) of those treated with sumatriptan improved in this way by 2 h, compared with 48% (118/246) of those treated with Cafergot (p < 0.001). The onset of headache resolution was more rapid with sumatriptan, whereas recurrence of migraine headache within 48 h was lower with Cafergot. Sumatriptan was also significantly more effective at reducing the incidence of nausea (p < 0.001), vomiting (p < 0.01) and photophobia/phonophobia (p < 0.001) 2h after treatment, and fewer patients on sumatriptan (24%) than on Cafergot (44%, p < 0.001) required other medication after 2 h. The overall incidence of patients reporting adverse events was 45% after sumatriptan and 39% after Cafergot; the difference was not significant. The most commonly reported events in the sumatriptan-treated patients were malaise or fatigue and bad taste; these were generally mild and transient. Nausea and/or vomiting, abdominal discomfort, and dizziness or vertigo were reported by a greater proportion of Cafergot-treated patients. It is concluded that oral sumatriptan was well tolerated and is a more effective acute treatment for migraine than Cafergot.