Links between parental knowledge and adolescent delinquent behavior were tested for correlated rates of developmental change and reciprocal associations. For 4 years beginning at age 14, adolescents (N = 396) reported on their delinquent behavior and on their parents' knowledge of their whereabouts and activities. Parents completed measures of their adolescents' delinquent behavior. Knowledge was negatively correlated with delinquent behaviors at baseline, and increases over time in knowledge were negatively correlated with increases in parent-reported delinquent behavior. Reciprocal associations indicate that low levels of parental knowledge predict increases in delinquent behavior and that high levels of delinquent behavior predict decreases in knowledge. Discussion considers both youth-driven and parent-driven processes that may account for the correlated developmental changes and reciprocal associations.