The purpose of this study is to examine the impact of the movement into early adolescence upon the self-esteem of children. Which children are most vulnerable to this role-transition and what is the effect of changes in school environment, pubertal development, and social behavior'? With repeated survey interviews and nurses' measurements, 798 school children were followed from sixth into seventh grade in two different types of school systems. Findings indicate that, in seventh grade, white adolescent girls who have entered the new environment of junior high school appear to be at a disadvantage in comparison both to boys in general and to girls who do not have to change schools. Among the girls, the ones with lowest self-esteem appear to be those who have recently experienced multiple changes, that is, who have changed schools, have reached puberty, and who have also started to "date." Among boys, in contrast, early pubertal development is an advantage for self-esteem. These data thus demonstrate the way in which coping with a major role transition can be significantly affected by environmental context, level of biological development, and social behavior.