This study represents the first to empirically validate the structure of social self-concept (SC) as proposed by the Shavelson model. For each of three age groups--preadolescents (252 3rd graders), early adolescents (290 7th graders), and late adolescents (335 11th graders)--analyses of covariance structures were used to test: (1) that social SC is both multidimensionally and hierarchically structured and (2) that causal direction underlying SC formation flows from social behavior at the base of the hierarchy, up through the network of social SC facets, to general SC at its apex. Results reveal a multidimensional structure that becomes more differentiated with age, but fail to yield any clear hierarchical pattern, regardless of age. Although the hypothesized direction of cause was strongly supported, and the structure of social SC basically similar across age, there were nonetheless several interesting developmental dissimilarities. Findings provide an important springboard for further construct validity research bearing on the structure and measurement of social SC. (Contains 74 references, 4 tables, and 7 figures.) (Author/SLD)