The aim of this study was to test the direction of effect in the relationship between parents' sources of knowledge (parental monitoring and child disclosure) and adolescent alcohol use. The participants were 215 adolescents and their mothers, randomly selected from urban and rural areas in Cyprus. A 3-month, two-timepoint longitudinal design was used in which adolescents completed the alcohol use disorders identification test while mothers completed a parental knowledge questionnaire. The results of this study showed that parental monitoring did not predict subsequent adolescent alcohol use. However, child disclosure at Time 1 negatively predicted adolescent alcohol use at Time 2. Moreover, adolescents' alcohol dependence symptoms at Time 1 negatively predicted both sources of parental knowledge at Time 2.