Using an eight-day hydraulics maintenance course taught by 121 instructors on a regular basis to classes of about 14 students using the same classrooms and materials, the Air Force conducted a study designed to determine instructor measures which correlate with, and are therefore predictive of, student achievement. The study report first discusses the problem of measuring student achievement, including the "ceiling effect" induced by inadequate precourse tests, the contamination of test results and rating measures, and the frequent lack of adequate samples of teachers imparting the same subject matter to similar students in the same learning environment. A description of the study methods and instruments follows, by which student gains criteria (as measured by a pre-course exam, a written post-test, and a performance examination) are correlated with instructor variables determined by peer and supervisor evaluation and by tests used to measure instructors' subject knowledge and general intelligence. The report then outlines the statistical criteria interrelations and validities and summarizes the study conclusions. Major findings include the result that students' ratings of instructors' subject knowledge produced significant correlation with instructors' proficiency tests while peer and supervisor ratings did not significantly correlate with student gains criteria. (JP)