The purpose of this study was to evaluate the efficacy of topiramate in the treatment of chronic migraine. This was a double-blind, randomized, placebo controlled, parallel-group study. Patients suffering from chronic migraine with analgesic overuse were randomly assigned in a 1 : 1 ratio to receive topiramate or placebo. Following a baseline phase of eight weeks, the study drug was titrated in 25-mg increments over one week to 50 mg daily. Titration phase was followed by a 8-week maintenance phase. Number of days with headache during a 28-day period was the efficacy variable. At baseline, there was no difference in the number of days with headache between patients treated with topiramate and those treated with placebo (mean +/- SD: 20.9 +/- 3.2 and 20.8 +/- 3.2, respectively). During the last 4 week-maintenance phase, topiramate-treated patients experienced a significantly lower 28-day headache frequency in comparison to those treated with placebo (mean number of days with headache +/- SD: 8.1 +/- 8.1 vs. 20.6 +/- 3.4, P < 0.0007). Topiramate at low doses proved to be an effective therapeutic approach to reduce headache frequency in patients with chronic migraine and analgesic overuse.