Topiramate (TPM) has shown efficacy in migraine prophylaxis in two large placebo-controlled, dose-ranging trials. We conducted a randomised, double-blind, multicentre trial to evaluate the efficacy and safety of two doses of topiramate vs placebo for migraine prophylaxis, with propranolol (PROP) as an active control. Subjects with episodic migraine with and without aura were randomised to TPM 100 mg/d, TPM 200 mg/d, PROP 160 mg/d (active control), or placebo. The primary efficacy measure was the change in mean monthly migraine frequency from the baseline phase relative to the double-blind treatment phase. Five hundred and seventy-five subjects were enrolled from 61 centres in 13 countries. TPM 100 mg/d was superior to placebo as measured by reduction in monthly migraine frequency, overall 50% responder rate, reduction in monthly migraine days, and reduction in the rate of daily rescue medication use. The TPM 100 mg/d and PROP groups were similar with respect to reductions in migraine frequency, responder rate, migraine days, and daily rescue medication usage. TPM 100 mg/d was better tolerated than TPM 200 mg/d, and was generally comparable to PROP. No unusual or unexpected safety risks emerged. These findings demonstrate that TPM 100 mg/d is effective in migraine prophylaxis. TPM 100 mg/d and PROP 160 mg/d exhibited similar efficacy profiles.