The purpose of this investigation was to determine the effects of training preservice elementary school teachers to use Bloom's Mastery Teaching Strategy. Data were collected and analyzed to determine the effectiveness of the training in three areas: a) affective change among the trainees with regard to tests, b) the ability of the teachers to apply the skills they learned in an actual school-teaching situation, and c) the effects of the training on the achievement and attitude of elementary school pupils. The results of the study show that because of the training a) teachers registered a more positive attitude toward the use of tests in evaluation; b) teachers could effectively implement mastery teaching strategies in the classroom; and c) pupils show no significant difference in achievement or attitude measures, although this may be due to the fact that the same teacher instructed both the control and experimental groups using different strategies and may have subtly and unknowingly utilized the experimental strategy while teaching the control group. (Author/HMD)