An important force combatting crime consists of the help and cooperation that citizens provide to the victims of crime and to the criminal justice system. This paper analyzes such behavior in light of economic theories of altruism. Using survey data on responses to questions about hypothetical situations involving various crimes, the analysis provides support for explanations of helping based on purely altruistic behavior, cooperative behavior based on self-interest, and behavior guided by social norms. Specifically, income, wealth, age, and race are found to be important in explaining helping behavior. © 1980, All rights reserved.