The purpose of the study was to determine the effects of class size and the use of teacher aides on pupil behavior and teacher behavior in educable mentally handicapped classes at the primary and intermediate grade levels. In the course of the study 20 classes remained constant and 18 aides were employed throughout the project. Effects on pupil behavior were determined by contrasting the educational and linguistic achievement and social behaviors in the several instructional arrangements. Researchers concluded that the major impact of the aides alone appeared to be a reduction in undesirable behavior in the classroom and an enhancement of the spelling achievement; class size alone had an effect on arithmetic and classroom behavior, with the standard classes gaining more in math and manifesting less negative behavior than the increased classes. It was generally felt that the most pronounced effects of the study appeared in the primary classes and suggested to the researchers that administrative strategies other than aides and class size should be developed to enhance the behavioral, linguistic functioning of intermediate educable mentally handicapped pupils. (CD)