Plasma testosterone levels were determined radio-immunologically in 57 men, including 23 patients suffering from cluster headache where the tests were carried out during the exacerbation of the disease but between the fits, 10 patients with trigeminal nerve neuralgia, 10 with radicular pain and 14 blood donors. Only in blood donors the normal plasma testosterone level was found and in the remaining tested groups this level was lowered in a statistically significant degree, the lowest values were observed in patients suffering from radicular pain. It is suggested that during cluster headache the level of testosterone is lowered but this is associated with repetitive pain seizures and not with the processes involving hypothalamus.