Prader-Willi syndrome is caused by a deletion of 15q11–13 or maternal disomy of chromosome 15. A female patient with Prader-Willi syndrome, who was 19 years of age at the first onset of her recurrent brief episodes, is described. The episodes showed a near-monthly rhythm and were followed by a spontaneous remission in 7–18 days. The symptoms during the episodes were anorexia, insomnia, guilt feelings, ideas of being doomed, ostracized and persecuted, and stupor alternating with agitation.