A military research study focused on the cost of on-the-job training (OJT) for enlisted men until they reach the proficiency level of journeyman, with objectives to develop a costing methodology for OJT sufficiently general to be used in almost any occupational specialty in any of the services and to pilot test that methodology and evaluate its usefulness. The method developed is a straightforward application of human capital theory in which the military's investment in OJT is measured as the present value of the sum of positive differences between an individual's military pay and productivity over time. Data for the pilot study of the method of estimating costs of OJT were collected at Norton Air Force Base, California, in the fall of 1972. The usable sample was drawn from approximately 700 men in the occupational group Aircraft Maintenance Specialists, the largest Air Force specialty, with the final sample for analysis consisting of sixty-four individuals based on the survey responses of twelve supervisors. The results in the pilot study indicate that the method gives plausible estimates of the magnitude of OJT costs and their relationship to trainee attributes. Measured mental ability and previous education were found to be importantly related to OJT costs, and the "typical trainee" approach of estimating costs of OJT was shown to give seriously downward-biased estimates. (VB)