This study extends the classic constructive dialogue/debate between self-concept and self-efficacy researchers (Marsh, Roche, Pajares, & Miller, 1997) regarding the distinctions between these 2 constructs. The study is a substantive-methodological synergy, bringing together new substantive, theoretical, and statistical models and developing new tests of the classic jingle-jangle fallacy. We demonstrate that in a representative sample of 3,350 students from math classes in 43 German schools, generalized math self-efficacy and math outcome expectancies were indistinguishable from math self-concept, but were distinct from test-related and functional measures of self-efficacy. This is consistent with the jingle-jangle fallacies that are proposed. On the basis of pretest variables, we demonstrate negative frame-of-reference effects in social (big-fish-little-pond effect) and dimensional (internal/external frame-of-reference effect) comparisons for three self-concept-like constructs in each of the first 4 years of secondary school. In contrast, none of the frame-of-reference effects were significantly negative for either of the two self-efficacy-like constructs in any of the 4 years of testing. After controlling for pretest variables, each of the 3 self-concept-like constructs (math self-concept, outcome expectancy, and generalized math self-efficacy) in each of the 4 years of secondary school was more strongly related to posttest outcomes (school grades, test scores, future aspirations) than were the corresponding 2 self-efficacy-like factors. Extending discussion by Marsh et al. (1997), we clarify distinctions between self-efficacy and self-concept; the role of evaluation, worthiness, and outcome expectancy in self-efficacy measures; and complications in generalized and global measures of self-efficacy.