The prevalence of cluster headache (CH) in the Republic of San Marino (21,792 inhabitants; 10,893 men and 10,899 women) was studied, reviewing the past 15 years' medical records of neurological, ophthalmological, and otorhinolaryngological services. Further cases were searched for by means of a letter sent to each inhabitant. Control of the case collection method was performed on a random sample of 1314 inhabitants over 7 years, interviewed for possible past or present cluster headache. We found 15 cases of CH (14 men, 1 woman), for an estimated prevalence ratio of 69 cases per 100,000 population. No previous reports have been published on the prevalence of CH in the general population.