A female patient is described who had a four year long period of unilateral chronic paroxysmalhemicrania (CPH) which then became bilateral. For some years before the CPH started she suffered fromperiods of about one month with chronic hemicrania without nerve involvement. She also suffered fromchronic fatigue, back pain, arthralgia, vertigo, chronic constipation and spontaneous ecchymoses. Bloodtests showed chronic leukocytosis, low serum iron, and signs of inflammation in serum electrophoresisduring the five years she was studied. CPH attacks could be provoked by breathing 6% carbon dioxide inair. Lumbar cerebrospinal fluid pressure was pathologically increased (30 cm water). The attacksdecreased during indomethacin treatment but 275 mg was needed for satisfactory control of the attacks,i.e., more than the 150 mg which, according to the criteria for CPH, should be absolutely effective.Sumatriptan was found to suppress the CPH attacks as well as indomethacin. Due to these findings CPH isconsidered to be another manifestation of venous vasculitis. The beneficiary mechanism of indomethacinin CPH is considered to be due partly to its anti-inflammatory effects and partly to its reduction of theintracranial blood flow.