The efficacy of feverfew capsules on migraine prophylaxis was investigated in a randomized double-blind, placebo-controlled crossover study in which 50 patients, who had not used feverfew before, participated. The capsules were filled with a dried alcoholic extract of feverfew on microcristalline cellulose and contained 0.5 mg parthenolide. The patients used one capsule (feverfew or placebo) a day. Fourty four patients completed the 9 month study. Both treatment groups suffered the same number of migraine attacks. A prophylactic effect could not be demonstrated for our feverfew preparation, but the patients seemed to have a tendency to use fever symptomatic drugs during the period they used feverfew. This result was not in accordance with the results from two other studies. The difference may be explained by the fact that both other studies included patients who previously reported positive experiences with feverfew preparations for migraine prophylaxis.