The purpose of this study was to gain a clearer understanding of the relation between parents' knowledge of their emerging-adult children and emerging adults' risk behaviors. Participants included 200 undergraduate students between the ages of 18 and 25 (121 women, 78 men; M [subscript age] = 19.59, SD = 1.62) and both of their parents. Results revealed that knowledge of the emerging-adult child's activities varied as a function of parent- and child-reports, and that child outcomes associated with parental knowledge were generally positive, including less drinking, drug use, and risky sexual behavior (although this varied as a function of reporter). The links between maternal knowledge and lower drug and alcohol use were particularly strong in the presence of maternal closeness. Implications for understanding the parent-child relationship during the transition to adulthood were discussed.