In this paper we examine period or secular changes in the association between drug use and delinquency among Ontario adolescent students between 1983 and 1991. The results show that during this period drug use and drug-setting declined significantly, whereas reported non-drug-related delinquency increased. In addition to differing secular trends in rates of drug use and delinquent behaviour, the association between the two behaviours weakened. There was a steady decline in the correlations between drug use and delinquency across time, and the typological patterning of drug use and delinquency changed significantly.