This article provides a critical review of the extant literature on sleep & suicidality, & addresses shared underlying neurobiological factors, biological & social “zeitgebers”, treatment implications, & future directions for research. Findings indicate suicide ideation & behaviours are closely associated with sleep complaints, & in some cases, this association exists above & beyond depression. Several cross-sectional investigations indicate a unique association between nightmares & suicide ideation, whereas the relationship between insomnia & suicidality requires further research. Unlike other suicide risk factors, sleep complaints may be particularly amenable to treatment. (57 refs.)