The author first examines different research approaches for examining the relationship between depression and homicidal behavior. Following a review of the limitations of such studies, the author concludes that the studies are significant in supporting a hypothesis for an increased susceptibility to violence in someone with a psychotic major depression. This is followed with a discussion of clinical manifestations of a psychotic major depression. Topics addressed are the irrelevancy of neurotic/endogenous division, the significance of delusions and hallucinations, diagnostic approaches, and the murder-suicide phenomenon. The author's proposed hypothesis is that when a depressed person commits a homicide, the act is likely to be connected with the presence of psychotic thinking; more specifically, it is a response fostered by a thinking disturbance. In connection with this hypothesis, the article discusses the role of anger and provocation, the emergence of delusional thinking, catathymic states, and final pathways. Future research problems are also identified. 53 references