During 1981-96 a series of 60 consecutive out-patients was examined in relation to an assumed first period of cluster headache (CH). On follow up in 1998 we found that six were deceased at a mean age of 56.5 years (range 45-74 years), of whom one had a definitive CH diagnosis and five had one documented headache period only. Six patients were lost to follow up because they could not be reached. In the final group for evaluation (n = 49) it was found that 13 (26.5%) patients had had one cluster period only during a mean observation time of 8.9 years. Out of 36 patients with a definitive CH diagnosis according to International Headache Society (IHS) criteria, 31 patients had episodic CH, four patients had primary chronic CH and one patient had secondary chronic CH. Of the patients with a definitive CH diagnosis, 83% on follow up had had a recurrence of a second period of CH within 3 years or continuous attacks (chronic/semichronic CH) from the onset. Evidently some patients may suffer from one cluster period only. In our patient material only 17% had a second cluster period after 3 years.