The literature on menstrual psychosis is briefly reviewed in this article. There are about 80 cases with substantial evidence, and about 200 other possible cases. The clinical features are generally those of manic depressive (bipolar) disorder. The diagnosis requires the accurate dating of the onsets of episodes and of menstrual bleeding. Obtaining a baseline of several carefully dated episodes is also important in finding the best way to arrest the periodic illness. Although conventional psychotropic drugs can shorten episodes, they do not prevent recurrences. For this, unconventional treatments appear to be more effective, especially thyroid hormone and clomiphene. Patients with menstrual psychosis usually have abnormal menstruation, such as anovulatory cycles, luteal defects, or periods of amenorrhea. This, and the occurrence of episodes before the menarche, suggests that the interaction between the bipolar diathesis and menstruation is in the hypothalamus.