A definition of self concept as the individual's perception of how he is perceived by others whom he believes to be significant (important) was used as a basis for defining and assessing self concept in the present study. A number of questions associated with development and the stability of self concept were examined. These include: (1) the extent to which self concept differs as a function of socioeconomic level, an individual's perception of significant others, and the interaction of cultural level and an individual's perception of significant others; (2) the extent to which self concept of an individual varies as a function of his perception of significant others; (3) how the self concept of an individual varies as a function of his sex, age, and the interactions of his significant other and sex and age; and, (4) how self concept varies as a function of the absence of one parent. The subjects for this study were 458 students in grades, 4, 8, and 12 selected at random from two school districts in central Pennsylvania. Two measuring instruments, the Referent Questionnaire and the Student Opinion Poll, were administered. An analysis of variance of self concept data was completed using three factorial designs. That school age subjects tend to have the most positive self concepts when they are (1) socioeconomically advantaged and have parents as chosen significant others or (2) socioeconomically disadvantaged and have peers as the chosen significant others was among the major findings. (Author/JM)