One hundred and forty-eight student teachers from Israel Institute of Technology were subjects of an experiment investigating effectiveness of microteaching alone as compared with a category observation system as a training method, and interaction between the two when combined. Thirty-two subjects were assigned at random to each of the four cells of the 2 x 2 factorial design. Data was gathered by the Technion Diagnostic System (TDS) category observation instrument. Analysis of covariance results lead to the conclusion that while microteaching improves simple technical skills, TDS feedback of the entire lesson produces better results in achieving higher level objectives, even better than the combined use of the two systems. (Author)