Some early psychiatrists already believed that schizophrenic disorders were associated with a disturbed balance of sexual hormones. This belief was based on the observation of a. an "insufficient functioning of the sexual glands" with so-called "hypoestrogenism", and b. an influence of ovarian function on schizophrenic psychoses. As this review shows, there are findings from recent research which seem to confirm that estrogens may have a protective effect in schizophrenia. There are also occasional hints at a possible "hypoestrogenism" in schizophrenia. In our own epidemiological, clinical and animal studies the hypothesis of a protective effect of oestrogens was for the first time systematically examined and confirmed. Oestrogens seem to modulate the sensitivity of D2-receptors in the brain, and clinically they seem to have a neuroleptic-like effect. These findings may have important implications for the prevention and therapy of schizophrenic disorders. Furthermore, our findings indicate the need to reinvestigate the question of a disturbed balance of sexual hormones in schizophrenic disorders. Further research on the role of oestrogens in schizophrenic disorders could in our opinion contribute to understanding the still unclear, possibly aetiologically heterogeneous pathogenetic mechanism of schizophrenic psychoses.