This is a part of a three year longitudinal study on the physical and psychological development of Chinese school pupils. A total of 687 youngsters (335 males, 352 females) were sampled from two elementary schools and two junior high schools in Taipei. The self concept scale, followed the Tennessee Self Concept Scale, was administered to the subjects twice in the regular class settings (one year interval). This study treated the year´s changes of scores of self concept scale as criteria, sex and grade level as independent variables, the statistical analyses revealed that: 1. The self concept characteristics of elementary school boys and girls, and junior high school male students did not change with age while some of self concept characteristics of junior high school female students descended with age. 2. The sex differences of changes of self concept characteristics were not significant in elementary school, the same was found in junior high shool, except one of those characteristics family self. 3. The effects of grade level on the changes of self concept charatericstics were not significant for males and females.