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 between self-reports by parents and the reports by their children varied between 0.56 (P