This study tested assumptions and conclusions reached in an earlier confirmatory factor analysis (CFA) study of the social competence (SC) construct for preschool children. Two samples (total N = 408; a new Portuguese sample and one from US samples that had participated in the original study) contributed data. Seven SC indicators were tested for mean differences across age, sex, and sample. Significant sex differences were found for peer acceptance (favoring girls) and for initiating affectively neutral interactions (boys had higher rates), and the sex by sample interaction also was significant for initiating interactions (i.e., effect significant only in the Portuguese sample). In CFAs, the hypothesized structure of SC fits the data and was invariant across sample and age within sample in both measurement and structural tests. The model was invariant at the measurement level for sex within sample tests, but not at the structural level. The results replicate and extend understandings of SC reported in the original study. (Contains 4 tables and 1 figure.)