Two intermediate algebra classes at a large university were selected for this study comparing increase in mathematics achievement for students enrolled in a course that used either traditional lecture approach or a traditional lecture approach plus a mastery learning laboratory. The laboratory was staffed by tutors who administered and graded unit tests and provided tutoring. Students were required to pass unit tests with scores of at least 90% before taking the next unit test; if not, they returned later to take another version of the test. Students were assessed pre- and post-instruction in terms of achievement and attitudes toward mathematics. Findings indicated that the students in the mastery learning plus lecture approach achieved higher final examination scores and tended to have higher scores on a standardized algebra test when prior mathematics background was held constant. They also tended to have a more positive attitude toward mathematics and greater awareness of the importance of mathematics than did those students in the lecture-only approach. Implications for teacher education programs are discussed. (JD)