The aim of this study was to examine gender-related differences in electroen-cephalographic (EEG) sleep in inpatients with psychotic disorders. We investigated the effects of gender and age as well as gender-by-age interactions on sleep continuity, architecture and intranight distributions in 38 male and 23 female patients with functional psychoses. No gender effects were seen for any sleep parameters. However, older psychotic males had less slow-wave sleep than older psychotic females. On the other hand, female psychotic patients showed a significant decline in automated REM counts with age. It is possible that gender-related differences in neurodevelopment and/or aging could account for these findings.