This study's hypothesis is the 4mg StatDose sumatriptan is effective for the acute treatment of cluster headache and provides good safety and tolerability across multiple doses of the study medication as well as across multiple attacks of cluster headache. This study seeks to determine the safety and efficacy of the commercially available 4mg StatDose formulation of sumatriptan as an acute treatment of cluster headache. Patients are allowed to use repeated dose of the study medication for a given headache if they have had a partial response to the first dose. They may treat up to 3 attacks of cluster headache with the study medication. Safety assessment will be through adverse event reporting and physical examination. Patients with both episodic cluster headache as well as chronic cluster headache will be studied. Patients must either not have started preventive treatment for cluster headache or be on a stable dose of preventive medication.