The internal/external (I/E) frame of reference model describes relations among Verbal self-concept (VSC), Math self-concept (MSC), and corresponding achievement scores (VACH, MACH). In support of the model Marsh (1986) found that: (1) VSC and MSC were nearly uncorrelated; (2) the effect of VACH on VSC, and of MACH on MSC, were positive; but (3) the effects of VACH on MSC, and of MACH on VSC, were negative (higher skills in one area lead to lower self-concepts in the other area). However, the support was limited to responses just to the Self Description Questionnaires by Australian subjects. In the present investigation the findings were replicated with each of three different self-concept instruments for responses by Canadian senior high school students. An extension of the original model to include school grades across all classes, school self-concept, general self-concept, and gender did not affect support for the I/E model. However, this extension provided remarkably strong support for the specificity of multiple dimensions of self, and perhaps for the influence of sex stereotypes on academic self-concepts beyond what can be explained in terms of academic achievement. (Author)