The computational model of Slater, based on the analysis of ancestral secondary cases on the paternal and maternal sides of the subjects, was applied to depressed patients with a lifetime history of attempted suicide, either violent or nonviolent, in order to investigate possible modes of transmission of suicidal behavior. Among 549 patients, 15 had 2 or more ascendant first- and second-degree relatives who committed suicide. The results of the distribution of these cases were compatible with polygenic inheritance of suicidal behavior in depressed patients with a history of attempted suicide. In patients using violent methods, a significantly greater loading of ancestral secondary cases of suicide was observed on the maternal side and, in the nonviolent attempter group, on the paternal side.