Hypnic headache syndrome is a benign, recurrent, late-onset headache disorder that occurs exclusively during sleep. Lithium has been reported to be an effective treatment, but the side effects of this medication are sometimes prohibitive, particularly in the elderly. Other drugs have been reported to be effective in this disorder, including caffeine, flunarizine, and verapamil. Recently, indomethacin has been reported to effectively suppress hypnic headaches. We report the response of seven patients with hypnic headache who were treated with indomethacin. Hypnic headache syndrome appears to represent yet another headache disorder in which there is sometimes an impressive response to indomethacin.