In research concerning socialization into sports there is a need to assess children's reports of parental physical activity. Reports by young adolescents and their parents of each other's leisure-time physical activity and related issues were compared with self-reported measures. A total of 755 family units in western Norway, consisting of 755 13-year-olds, mean age 13.3±0.3 years (425 boys, 330 girls, 644 fathers and 732 mothers) completed a self-administered physical activity questionnaire. Pearson's r between self-reports by parents and the reports by their children varied between 0.56 (P<0.001) and 0.07 (nonsignificant). Pearson's r between off-springs' self-reported physical activity and reports by their parents varied between 0.41 and 0.55 (P<0.001). The results support cautious use of young adolescents' reports of parental physical activity.