Adoption and twin studies show that familial transmission of suicidal behavior is partly attributable to genetic factors. Transmission of suicidal behavior is mediated by transmission of impulsive aggression or neuroticism and neurocognitive deficits. The most plausible explanations for nongenetic familial transmission are the intergenerational transmission of abuse and adverse familial environments. Bereavement and relationship disruption contribute to suicidal risk via the development of complicated grief, although long-term effects may be mediated by a complex chain of interrelated events. Imitation may contribute to suicidal risk, at least in attempted suicide. However, so-called family environmental factors often are related to risk factors that are heritable. Conversely, genetic factors exert their impact on depression and suicidal behavior via interaction with a stressful environment.