Early maternal separation is a particularly stressful experience. Current models of nightmare production emphasize negative emotionality as having a central role in determining dream affect. Our aim is to test the hypothesis that persons who experienced early maternal separation (before one year of age and lasting at least one month) report more frequent nightmare experiences and bad dreams as adults. In the frame of the Hungarostudy Epidemiological Panel, 5020 subjects were interviewed. Significant associations were found between early maternal separation and both frequent nightmare experience in adulthood and increased frequency of oppressive and bad dreams. Current depression scores fully mediated the association between early separation and nightmares, but not the association between early separation and negative dream affect. We interpret these findings as a trait-like enhancement of negative emotionality in adults who experienced early maternal separation. This enhancement influences the content of dreams and, when it takes the form of depression, also influences the frequency of nightmares.