This study tested the efficacy of brief image-based print-mediated parent/caregiver and adolescent messages integrating physical activity with alcohol use avoidance. A total of 684 high school students were randomly assigned to either the parent postcard or adolescent flyer arm, with baseline and four-month postintervention data collections. A significant repeated measures interaction (group x time) was found (F(4,344) = 2.48, p = 0.04), with univariate tests showing less alcohol use frequency and problems (ps less than 0.05) among adolescents exposed to parent materials. Repeated measures factorial MANOVAs for group x time x prior current drug use were significant, with drug using adolescents receiving parent print messages showing less alcohol initiation and frequency and marijuana initiation and frequency (ps less than 0.05). Very brief print materials sent to parents/caregivers may hold some promise for influencing substance use among adolescents, particularly those already using drugs. (Contains 2 tables.)