An approach to evaluating the appropriateness of student effort within a mastery instructional system was developed, and the interrelationship of achievement motivation, effort and achievement was investigated. In support of a prominent theory of classroom learning, appropriate effort was strongly correlated with student achievement even when differences in student aptitude were controlled. Finally, achievement motivation was shown to be related to both the effort and achievement variables. A path analysis indicated that the influence of achievement motivation on achievement was determined primarily by the relationship of achievement motivation and effort. (Author)