The first section of the chapter reviews the few recent attempts to expand the model of homicide and suicide developed by Henry and Short, which links both suicide and homicide to aggression that stems from frustration; the latter arises from restraints that prevent individuals from reaching goals central to their core needs. The second section of the chapter discusses comparative studies of lethal violence at the national or cross-national level. The third section examines research that compared homicide and suicide rates among social and demographic groups, such as whites and Blacks, or tested the importance of explanatory variables, using data from the United States. The fourth section briefly examines recent studies of suicide and interpersonal aggression in the fields of biology and medicine. Although these ideas have arisen independently of and to some extent in opposition to sociological traditions, they are nonetheless more consistent with the stream analogy (links suicide and homicide in a "stream" of violent impulses) than they appear at first glance. The final section of the chapter reviews a body of research, much of it based in the public health field, which examines commonalities between homicide, suicide, and accidents. The authors conclude that there is scant evidence of cumulative progress in developing an understanding of the sources of lethal violence or the factors that influence its direction during the past two decades. They believe that the pace of cumulative advances in research on lethal violence will be quickened by the establishment of an integrated theoretical perspective that provides linkages between studies that appear in separate disciplines. They contend that Henry's and Short's work, if properly understood from the perspective of the stream analogy and updated to reflect developments in other areas, provides a model for investigating the social sources of lethal violence at the individual and aggregate levels.