Hirschi and Gottfredson (1983; Gottfredson and Hirschi, 1990) have argued that the age distribution of crime cannot be explained by any known variables. and they point specifically to the failure of sociological theories to explain this phenomenon. This paper examines a quintessentially sociological theory of crime—differential association—and evaluates its ability to explain the age distribution of crime. Analysis of data from the National Youth Survey on persons aged 11–21 reveals that peer relations (exposure to delinquent peers, time spent with peers, loyalty to peers) change dramatically over this age span, following much the same pattern as crime itself When measures of peer influence are controlled, the effects of age on self-reported delinquency are largely rendered insignificant. Additional analyses show that delinquent friends tend to be “sticky” friends (once acquired, they are not quickly lost) and that Sutherland's arguments concerning the duration and priority of delinquent associations are only partially correct.