The purpose of this study was to examine the influence of Bandura's (1997) hypothesized sources of self-efficacy on the academic and self-regulatory efficacy beliefs of entering middle school students ("N" = 263) and to explore whether these sources differ as a function of gender, reading ability, and race/ethnicity. For the full sample, mastery experience, vicarious experience, social persuasions, and physiological state independently predicted academic and self-regulatory self-efficacy, with mastery experience proving the strongest predictor. Mastery experience and social persuasions predicted girls' academic and self-regulatory self-efficacy, whereas mastery and vicarious experiences predicted these self-beliefs for boys. African American students' mastery experiences and social persuasions predicted their academic self-efficacy. Mastery experience did not predict the self-efficacy beliefs of low-achieving students. Findings support and refine the theoretical tenets of Bandura's social cognitive theory.