A study was conducted to determine if training to increase teachers' observable level of enthusiasm had a subsequent effect on student achievement and attitudes toward the teacher and curriculum. Seventeen first-year elementary teachers were randomly assigned to either an enthusiasm training treatment or a no training treatment. Following the training phase, all teachers taught a two week controlled unit in mathematics to their classes. Results indicate that trained teachers increased significantly on eight indicators of enthusiasm compared with untrained teachers. However, students of trained and untrained teachers did not differ either on the achievement post-test or on the attitude scales. Analysis of the controlled instructional unit suggests an explanation for the similarity in posttest achievement of the experimental and control classes. The effect of teacher enthusiasm may have been minimized because students were enthusiastic about unit content and materials. Also, the instruction period was too short, and the achievement posttest too distal for teacher enthusiasm to affect it. Further research is suggested to determine the trainability of teacher enthusiasm and its empirical effects on student attitudes and achievement. (Author/GK)