Cluster headache is characterized by excruciatingly painful headaches which occur one or several times during the day. Little is known about the functional consequences of this severe headache form. We assessed health-related quality of life in 56 consecutive patients, 34 of whom were episodic cluster headache patients during an active period, and 22 had chronic cluster headache. All patients completed the Short Form-36 (SF-36). We found lower scores in the studied patients than in those reported in the general population for all SF-36 domains. For most scales the difference was significant (P < 0.0001, Student's t-test, Bonferroni correction). Our findings suggest that cluster headache has marked functional consequences even when appropriate treatments are used.