The interrelations of psychological functioning and endocrine and physical growth factors in young adolescents are investigated. Participants are 56 boys and 52 girls, 9 to 14 years old, and their parents. Participants were evaluated three times, six months apart, on stage of pubertal development (Tanner criteria), hormone levels, and psychological status and behavioral functioning, including interactions with their parents. Relations between behavioral and hormonal changes in a potentially stressful situation (blood withdrawal and physical examination) and adjustment problems were examined. Parental support in relation to amount of distress behavior shown in the stressful situation was also examined. It was hypothesized that adolescents who showed high physiological reactivity (increase in cortisol level during the stressful procedure) would have more behavior problems and symptoms of anxiety and depression one year later than adolescents who showed no change or decrease in cortisol level. The hypothesis was partially supported. Adolescents who showed increases in cortisol level reported more non aggressive behavior problems and more depressive symptoms one year later than the adolescents who showed no change or decrease in cortisol level. There were no differences among the groups on aggressive behavior problems or symptoms of anxiety. Also, parents showed more monitoring and regulating behavior toward adolescents who showed the most behavioral distress. Parental anxiety was positively related to adolescent cortisol level. Parents of boys showed distress to signs of behavioral distress in their child; parents of girls did not show this type of response.