The purpose of the study was to evaluate the effectiveness of an instructional unit on agriculture/agribusiness management in Iowa vocational agriculture classes. A pretest-posttest, control group design was used in the investigation. Sixteen vocational agriculture classes comprised the experimental treatment group, whereas twelve classes provided data for the control group;Experimental group instructors were provided an agriculture/agribusiness management instructional unit and directed to use the approach suggested in their teaching. Control teachers were asked to focus their teaching on a list of problem areas and study questions upon which the instructional unit was based;Four instruments were developed and used to collect data needed to assess the effectiveness of the instructional unit. Knowledge and attitude inventories were administered to students as both pretests and posttests. Student and teacher data instruments were completed by respondents only at the end of the experiment;Class means were analyzed as they were comprised of the experimental units which were initially selected. T-tests and analysis of variance were the main statistical procedures used in the study to test for mean differences;The intent of the study was to test the approach suggested in the instructional unit. Participating teachers were selected by the researcher on the basis of their ability to provide an unbiased test of the materials. Conclusions and recommendations resulting from this investigation should be interpreted with caution as generalizations are limited to participating students, teachers, and classes. Implications may be extended to other groups on a practical basis;Major findings of the study were: (1) there was a difference ( p < .05) between pretest and posttest knowledge scores for both groups, (2) experimental classes increased their knowledge scores to a greater extent than did control classes during the experiment, (3) student attitudes toward agriculture/agribusiness management were essentially unchanged during the course of the experiment, and (4) experimental group teachers responded favorably to the quality and value of the instructional unit. These findings revealed the agriculture/agribusiness management instructional unit was effective in selected Iowa vocational agriculture classes.