The aim of this study was to analyze the factorial structure and the reliability of the Inventory of Self-concept Form “A” (AFA A) by Musitu, García and Gutierrez (1991) in a Mexican population. The questionnaire was applied to 2349 male and female adolescents from State and private Secondary schools with an average age of 13 years, pertaining to 18 schools in 10 districts from Mexico City and the Metropolitan Area. The inventory includes 36 items with three possible answers. The factorial analysis isolated four factors, which explain 31.94% from the total variance. The internal consistency is an Alpha of α=0,8. The conceptual congruence of items was analyzed and found to be consistent with Musitu et al’s (1991) proposal. Convergences and divergences derived from the analysis of the factorial structure of Mexican and Spanish populations are discussed.