We report on clinical experience with topiramate in the prophylactic treatment of three patients with chronic and two patients with episodic, otherwise therapy-resistant, cluster headache. Patients were treated with daily doses of 75-200 mg topiramate. Topiramate was effective in three patients but proved ineffective and also caused intolerable side-effects in two patients. Topiramate may have prophylactic properties for treating cluster headache at lower doses than needed in epilepsy therapy, but its clinical value is limited due to central nervous system side-effects.