This paper explores the effect of certainty of punishment on different types of criminal behavior. It is argued that deterrence theory, which treats the potential criminal as weighing the relative rewards and costs of a criminal act, is more applicable to certain types of crimes than others. The strength of the negative relationship between certainty of punishment and crime rate will thus vary by type of crime. It is argued that deterrence, overload, and incapacitation theories each predict different patterns of these variations in strength. Thus the fit of the expected pattern to available data should allow us to choose among the theories. Using previously unpublished data for SMSAs and results obtained by other researchers, the actual patterns of strength of relationships are studied. Though the data presently available have many problems and some of the patterns are ambiguous, the deterrence predictions seem to have the best overall support.