The study makes use of Rotter's (1966) hypothesis that there are consistent individual differences between people who believe in the internal control of reinforcement and those who believe in the external control of reinforcement. Students who are "internals" will believe that their behavior controls academic successes and failures and may, resultantly, participate more actively in class or allow adequate time for study. Externals are less likely to engage in such behaviors since they are not inclined to see their actions as having such effects on success or failure. Two separate investigations are reported which tested the proposition that students who act to maximize their chances of classroom success are more likely to be internal rather than external. Results of the first test, in which 499 introductory psychology students participated, indicated that, at the end of the course, internals had earned significantly more credit than externals. In the second test, using 169 comparable students, more internals were selected as high class participators than were externals. The hypothesis, thus, receives strong support. (TL)