Treatment with the histamine H2 receptor antagonist, cimetidine, alone and/or in combination with the histamine H1 receptor antagonist, chlorpyramine, in 13 patients showed that cimetidine alone was ineffective. 7 of 9 patients taking the combination of H1 and H2 receptor antagonists responded well to the treatment; in 1 patient, medication was ineffective and in 1 patient, success was doubtful. In 3 patients with chronic cluster headache, the effect faded after 4 weeks. The results are discussed.