It has been suggested that treatment of cluster headache (CH) patients with topical capsaicin may desensitize sensory neurons by depleting the nerve terminals of substance P. We attempted to determine whether capsaicin is effective in aborting CH attacks. Patients in acute cluster were randomized to receive either capsaicin or placebo in the ipsilateral nostril for 7 days. Patients recorded the severity of each headache for 15 days. Headaches on days 8-15 of the study were significantly less severe in the capsaicin group vs the placebo group. There was also a significant decrease in headache severity in the capsaicin group on days 8-15 compared to days 1-7, but not in the placebo group. Episodic CH patients appeared to benefit more than chronic CH patients. These results indicate that intranasal capsaicin may provide a new therapeutic option for the treatment of this disease.