Aim: To determine if botulinum toxin type A (BoNT-A) injections can reduce the frequency and severity of migraines. Methods: Patients (n = 127) were randomized to receive placebo or two doses of BoNT-A (Dysport (R)). The primary endpoint was reduction in number of migraine attacks up to week 8 and between weeks 8 and 12 after injection. Patient diaries were used to record secondary endpoints, including frequency, severity and duration of migraine attacks. Results: There was a mean reduction of 0.54 and 0.94 attacks/month with placebo and BoNT-A, respectively, and absolute attack count was less in the verum group (3.6 vs. 4.2 attacks/month), but this was not statistically significant. The patients' global assessment of efficacy was significantly better than placebo in the high-dose group (p = 0.02) but no effects were seen for the other secondary efficacy parameters. Conclusion: Our study showed a trend towards a reduced attack rate with verum but did not show any statistically significant efficacy of BoNT-A in the prophylactic treatment of migraine. Copyright (C) 2009 S. Karger AG, Basel