Data were collected through interviews with the murderers and their family, friends, employers, and therapists. The results showed that, while intoxication and substance abuse were common etiological factors contributing to homicide, they were not always present in such cases. In slightly more than half the cases, active substance abuse was present, and slightly less than half the murderers were intoxicated during the commission of their crime. Cluster analysis identified seven profiles of murderers. In two of these factors, accounting for 33 percent of the study subjects, substance abuse and intoxication were primary etiological factors. In three other clusters, comprising nearly 40 percent of the subjects, substance abuse tied with other etiological factors for preeminence. In the final two clusters, accounting for almost 30 percent of the subjects, substance abuse was not a significant factor. 13 tables and 20 references