Mastery learning is an approach to learning whereby students are expected to demonstrate competence of one level, or unit, of learning objectives before advancing to the next level. Most junior college instruction is group-paced, with the instructor determining the rate with which units are presented. One compromise between existing instruction and ideal mastery learning techniques is to provide specific supplementary instruction for those students who fail to master a given unit, while maintaining the group pace. The research reported focused on one form of that compromise: the effect of teaching one additional lesson per unit to those students who did not achieve mastery of that unit. Another part of the research examined the effect of providing students with detailed behavioral objectives. The research was conducted in selected English and algebra courses at five community colleges in Southern California. Dependent variables were scores on semester exam and mastery rates, as defined by the proportion of the number of students who received A's, B's, and C's to the total number enrolled. The results of the research are reported separately for the English and algebra classes. In the algebra classes, the students received testing and remediation for mastery, and they achieved significantly higher final exam scores than control students. There was no significant difference between mastery rates of experimental and control students. In the English classes, the students who received detailed behavioral objectives scored significantly higher on their final exam than did control subjects who did not receive the objectives. (Author/DB)