Suicide and suicidal behavior is highly familial, and appears to be familially transmitted independently from the familial transmission of psychiatric disorder per se (1). Adoption, twin, and family studies support the view that the etiology of the familial transmission of suicidal behavior is at least in part genetic, and may be mediated by the transmission of intermediate phenotypes, such as impulsive aggression. In addition, there may be environmental causes for familial transmission, including imitation, and the intergenerational transmission of family adversity. In this review, we cover the evidence supporting the familial transmission of suicidal behavior, possible genetic and environmental explanations for this phenomenom, describe putative intermediate phenotypes, and discuss the contributory roles of early child-rearing and concurrent familial environmental stressors to suicidal risk. A better understanding of the mechanisms for the familial transmission of suicidal behavior can help to shed light on etiology, identify individuals at high risk for the development of incident suicidal behavior, and frame targets for intervention and prevention.