The premenstrual and menstrual periods are associated with increased psychiatric disturbances, both of a psychotic and neurotic nature. Pre-existing psychosis can worsen in the premenstrual period, or, as we describe in the following case report, a psychosis can occur in the premenstrual period with complete remission once the bleeding has ceased. The role of menstruation in the timing and pathogenesis of the major psychoses is largely ignored in present-day psychiatry. In the nineteenth century, however, psychosis coincident with menstruation was thought to merit its own special term (Menstruationpsychose), and Kraepelin himself described the importance of the association (Kraepelin, 1909). In contrast, premenstrual tension has been the subject of continuous interest since the term was first used by Frank (1931), and there have been cases described of premenstrual tension in association with psychosis. Williams & Weeks (1952), for example, reported on 16 cases where the psychosis was characteristic of mania or catatonic schizophrenia, and more recently, Price & DiMarzio (1986) found that 60% of a group of rapidly cycling manic-depressive psychotics suffered from severe premenstrual tension. Psychosis associated with the menstrual cycle without concomitant symptoms of premenstrual tension has also been described. Lingjaerde & Bredland (1954) presented a case of a 24-year-old woman who developed a manic–depressive (manic-type) psychosis synchronous with her menstrual cycle, after childbirth. A Japanese cohort of patients diagnosed as suffering from “periodic psychosis” (Wakoh et al, 1960) showed significant correlation between acute psychosis and the luteal phase of the menstrual cycle. The premenstrual period is also known to exacerbate pre-existing psychosis; Ota et al (1954) and Gregory (1957) have shown a significant increase in psychotic behaviour in the last 10 days of the menstrual cycle. We present a patient with a schizophreniform psychosis occurring irregularly but concomitant with her menstrual cycle, with total remission during the interval stage.