This double blind, randomized study of the calcium antagonist Nimodipine 40 mg t.i.d. vs placebo in the prophylaxis of common migraine (migraine without aura) included 192 patients. Patients with 2–8 migraine days/4 weeks, age 18–60, who had no other types of recurring headaches except up to 6 interval headaches/4 weeks were included. The study was carried out at 11 European centers. After a 4 week run-in period, patients were randomly allocated to Nimodipine or placebo for 12 weeks (parallel groups). There were 19 drop-outs, 12 on Nimodipine and 7 on placebo, A gradual and marked improvement was seen both with Nimodipine and with placebo amounting to approximately 60% during the last 4 weeks. Statistical analysis on all included patients (intention to treat) revealed no difference between Nimodipine and placebo for migraine days (P = 0.69) or migraine index (p = 0.91). In patients “valid for analysis of efficacy” there were also no significant differences. Due to a very marked placebo effect and use of the parallel groups design, the present trial was not very powerful despite the large number of patients and a satisfactory compliance. We cannot rule out that Nimodipine might have up to 30% effect on a single main outcome parameter, but the uniform lack of response in all tested parameters makes this unlikely. Therefore Nimodipine probably has only a small or no effect in common migraine (migraine without aura).