The principal objective of this study was to evaluate the occurrence of various dissociative phenomena in patients with major depressive disorder (MDD) and their possible implications in manifestation and course of depression. We administered the Dissociative Experiences Scale (DES) and a self-questionnaire of life events to 27 patients with MDD and to 40 healthy participants in order to collect information on traumatic events. Patients who scored >or= 20 on the DES were also assessed to determine the presence of dissociative disorder. Patients with MDD reported a significantly higher mean score on the DES than the comparison healthy participants. In all, 12 out of 27 patients with MDD reported childhood trauma, and their mean score on the DES representing absorption and imaginative involvement was significantly higher than that of participants without childhood trauma. Also, 7% of our MDD patients were diagnosed with dissociative disorder during this study. The principal limitations of the study were its small sample size and the use of a nonstandardized trauma measure. These findings indicate that dissociative phenomena should not be overlooked in MDD. Screening methods and structured interview for dissociative disorders are useful in psychiatric and psychological practice. Further studies should analyze the role and clinical consequence of different forms of dissociation experiences.