The purpose of this study was to examine the effects of self-concept and anxiety in Japanese early adolescents who participated in an eight-day adventure camp, conducted in 1982 and 1983. The study used 155 sixth- through eighth-grade volunteers, ages 11 to 14. The paper describes the camp program and training for the main activity, a three-day mountain climb. The Children's Self-Actualization Scale, the State Anxiety Inventory, the State Anxiety Inventory for Children, and Adventure Program Anxiety Scale were used to measure self-concept and anxiety levels before and after camp. The children generally showed improved self-concept and achievement motivation but no significant change in self-confidence or "perceived self," one's concept of how others evaluate one. Females showed more positive change in overall self-concept and achievement motivation than males after participating in the camp, although no significant difference was demonstrated between the two with regard to positive self-concept change. The study concludes that adventure camp participants improve in self-concept, that they have psychologically stressful experiences before a three-day mountain climb, and that those who experience greatly reduced anxiety levels have greater improvement in self-concept over those whose anxiety levels are not greatly reduced. It is observed that 11 to 14 year-olds appear to be in a critical period for self-concept changes and that camp programs achieve best results by offering success experiences in a variety of activities. Study includes 7 tables, a 27-item reference list and ideas for further research. (TES)