Report on clinical and electrophysiological findings in four members of a family with acute intermittent porphyria in the remission period. One patient had suffered from repeated epileptic seizures of the grand-mal type since the age of 24 years. Generalized and multifocal epileptic potentials were found in her EEG. Two other members of the family, a man and a woman, were found electromyographically and neurographically to have a florid neuropathy with damage to the axon and the myelin sheath. Only the female patient showed manifest clinical signs of the polyneuropathy. The 4th member, who years previously had had abdominal colics and suspect biochemical signs of acute intermettent porphyria, was not striking either neurologically or in electromyographic and neurographic polyneuropathy screening at the time of the examination. Epileptic seizures and the symptoms of the polyneuropathy had a close connection with the menstrual cycle (two cases). Before and at the beginning of the menstruation a deterioration of the disease was observed. Problems of antiepileptic therapy in acute intermittent porphyria are discussed.