The compositional effects of relatively large young-adult cohorts on the total rate of serious crimes is well established. The more subtle effect of relative cohort size on age-specij7c crime rates, suggested by Richard Easterlin, is more controversial. The literature contains no adequate test of Easterlin ' s hypothesis as it relates to crime. To provide an adequate test of Easterlin ' s theory, this study includes age-speciJc rates and measures of relative cohort size and controls for age and period in an age-period-relative-cohort-size model. Using arrest data from the Uniform Crime Reports (Part I crimes) for the years 1960, 1965, 1970, 1975, 1980, and 1985, the analysis provides support for Easterlin ' s theory for property crimes, that is, for robbery, burglary, and larceny (but not for motor vehicle theft). Though these relationships were small in comparison to those between age or period and age-spec@ crime rates, they were generally statistically signij7cant and were replicated with data from 1962, 1967, 1972, 1977, 1982, and 1987. The relationships between relative cohort size and assaultive crimes provided little consistent support for Easterlin 's theory.The dramatic increase in serious crime rates in the United States during the 1960s and 1970s needs little documentation. Homicide rates, for example, increased from 5.1 per 100,OOO in 1960, to 7.9 in 1970, to 10.2 in 1980, before declining to 7.9 in 1985. Similar increases occurred for the other part I crimes included in the Uniform Crime Report (UCR) crime index. 1Researchers attribute the increases in the overall rates of violent crimes to a number of factors, for example, increased urbanization (Ferdinand, 1970), increased unemployment rates (e.g., Cohen et al., 1980; Fleisher, 1963 Fleisher, , 1966, the consumer price index (Fox, 1976), the proportion of young black males in the population (Fox, 1976), and the residential population density ratio *This paper was motivated, in part, by a talk entitled, "A Test of Easterlin's Explanation of Trends in Political Alienation," given by William M. Mason. He, obviously, bears no responsibility for any errors in my own applications and modifications of his methods. I am indebted to Patricia Gwartney-Gibbs for suggestions and a careful reading of an earlier version of this paper.The UCR index includes murder and nonnegligent manslaughter, forcible rape, robbery, aggravated assault, burglary, larceny-theft, and motor vehicle theft. Arson was not added as a Part I crime until 1979.