In an effort to support Carroll's premise that there might be a relationship between foreign language aptitude and the degree to which the learner is capable of coping with the pace of language instruction, this study describes the comparative effectiveness of predicting student language learning potential through the Pimsleur Aptitude Battery, teacher evaluations, and student self evaluations. A discussion of the project design includes information on details of (1) administering the aptitude battery to 1,587 first-year foreign language students in five Tucson public high schools, (2) the development of the language aptitude data for each individual, and (3) the results of the correlational studies. Five tables of statistical data supporting an outline of tentative conclusions precede a brief discussion of final conclusions. Comprising half the report are four appendixes comparing the two teacher evaluations of a student and the student self-evaluation with the aptitude profile and prediction. (AF)