As is evident from this brief review, the genetic study of violence is maturing at an ever-increasing rate; much more work is needed to examine specific molecular genetic markers and their associated phenotypes, particularly in subjects with juvenile onset. It is also becoming clear that more work is needed to help delineate the specific phenotypes that are being transmitted within families. It is unlikely that we will find a gene or genes that are both necessary and sufficient for the manifestation of aggression and violence. It is more likely that specific genes will be associated with discrete factors that either increase the risk for the expression of violence or that are components of the violent phenotype. Thus, in addition to continuing research that examines the role of specific genetic factors in the manifestation of violence, more work is needed that will help further develop the nosology of violence and related behaviors. As noted previously, an understanding of the inherited phenotype is critical in the study of any disorder. It is especially important in the study of complex behaviors such as violence in which there may be several behavioral components that comprise the complete diagnostic category.