The purpose of the present trial was to evaluate semi-standardized acupuncture efficacy in migraine prophylaxis. Twenty-eight subjects with migraine were randomized to the real or sham acupuncture groups. Semi-standardized and standardized minimal acupuncture were used, respectively, in the two groups of patients. They were all treated with 16 acupuncture sessions in 12 weeks. Both groups exhibited similar reductions in: percentage of patients with reduction of migraine>or=40% and >or=50% regarding frequency of migraine attacks, days with migraine, frequency of migraine attacks, average duration of a migraine attack, rate of rescue medication used, average headache severity rate and other parameters compared with the baseline period. Associated symptoms, such as nausea and vomiting, also showed equal estimates in both groups. These findings showed that semi-standardized acupuncture shows no difference from sham acupuncture in preventing migraine attacks.