A longstanding debate focuses on whether suicide and homicide rates walk hand in hand or whether they are reciprocally related. Much of the research on this issue investigates whether suicide or homicide predominates in certain geographic areas or whether they trend together over time. We theorize that the degree of social integration and social regulation associated with birth cohorts is negatively related to both of these forms of lethal violence. We develop a common explanation for shifts in the age distributions of homicide and suicide in the United States from 1930 to 2000. In this context, suicide rates and homicide rates walk hand in hand and their parallel movements are associated with two variables linked to social integration and regulation.