An experimental group of 53 senior high school business education students and a control group of 45 were used in a study to determine whether teachers trained to teach enthusiastically had a significant effect on vocational business education student achievement as measured by a cognitive test (Business Jargon multiple choice pre and post-tests). Twelve high and twelve low ability students were identified for special observation in both groups. At the conclusion of the course and tests, it was concluded that the students significantly increased their knowledge of Business Jargon, but that enthusiasm had no real effect on the achievement of high and low ability students as defined in the study. Some unidentified factor associated with instruction in the control group had a significant effect on the achievement of the low ability students. It was also concluded that teachers can be trained to alter their teaching behavior to exhibit enthusiasm while teaching. Among the eight appendixes is a 52-page section on the extension of the Brophy-Good Dyadic Interaction System. (AG)