The study examined discrepancies in mother and child reports of parental knowledge (PK) of a child's whereabouts, activities, and companions, as well as the extent to which discrepancies in reports of PK are related to child risk-taking behavior concurrently and prospectively across two time points. The sample consisted of 219 mother and early adolescent youth (M age = 11.0, SD = 0.8) dyads. Mother and child reports of PK significantly differed and, at both waves, scores on the risk taking composite related negatively to both mother and child reports of PK and positively to the discrepancy between the two reports. A significant interaction between mother and child reports was found at Wave 2, such that the relation between child reported PK and risk behavior was stronger when mothers reported high levels of parental knowledge versus low levels of parental knowledge. Prospective analyses indicated a main effect of mother report. (Contains 4 tables and 1 figure.)