The objective of this study was to determine the difference in teaching effectiveness between experimental and control teachers as a result of a coordinated inservice program. Subjects were 83 high school teachers of vocational agricultural and other vocational subjects. Results indicate that inservice programs with a substantial theoretical base that can be understood and applied by teachers seemed to help teachers be more effective. Three areas of inservice training that helped the experimental teachers be more effective were knowledge and application of teaching and learning styles, classroom environments, and teaching effectiveness competencies. Teacher identification of needs, based on observational and student data, and development of a plan to improve, had a significant effect on the experimental group of teachers. The 3-year duration of the inservice program had a positive effect on change of teacher behavior. (IAH)