The purpose of this study was to examine the association between sleep duality and suicidality in major depressive disorder. We evaluated 41 patients with major depression by using the Pittsburgh Sleep Quality Index (PSQI) and the Schedule for Affective Disorders and Schizophrenia (SADS) suicide subscale. We found that suicidal depressive patients had significantly higher scores of subjective sleep quality, sleep latency, sleep duration, habitual sleep efficiency and PSQI global scores than nonsuicidal patients. We also found significant correlations between the SADS suicide subscale scores and most measures of the PSQI. These data suggest that there is an association between poor subjective sleep quality and suicidal behavior in patients with major depressive disorder. (C) 1997 Elsevier Science Ltd.