The current study investigated the influence of substance involvement on the trajectory of delinquency. Data were from 625 Buffalo, NY males aged 16-19, interviewed three times at 18-month intervals. Hierarchical linear models were fit separately for respondents with increasing and declining delinquency. In the increasing group, aIcohol involvment was associated with a higher starting point (intercept), and alcohol dependence and drug consequences were associated with a faster increase. In the declining group, alcohol dependence and drug consequences were associated with a higher starting point, and frequency of drug use was associated with a slower decline. Alcohol involvement is important in the early delinquent career whereas illicit drug use delays maturing out of delinquency. In a further analysis, substance involvement variables were time-varying covariates in the within-subjects model and controls in the between-subjects model. Respondents' alcohol and other drug use varied across time in sync with their criminal offending.