The authors examined 52 women with recurrent depression to determine the differences between women with and without histories of pregnancy-related affective episodes. The women with histories of such episodes (N = 24) had been significantly younger at illness onset, were more severely depressed at baseline, and tended to show less emotional stability. The EEG-recorded sleep of the women with pregnancy-related affective episodes was distinguished by longer REM sleep time and more REM activity, differences accounted for almost entirely by the women with histories of only postpartum episodes.