To examine the economic efficiency of initial military specialty training, procedures were tested for estimating the effects of that training on posttraining job performance. The approach chosen was an application of human capital theory in which the costs of on-the-job training and the returns to training are measured by comparing the trainee's pay and net productivity. The key element in implementing this approach is the estimation of on-the-job productivity. The data used to explore the tradeoff among training courses of different lengths consisted of enlisted supervisors' estimates of the net productivity of trainees at different points in their first term of military service. These estimates were used to construct profiles of the time path of productivity. All the productivity curves for the six specialties examined showed a positive slope that tended to decrease over time (the rate of improvement declining with experience). Moreover, comparisons among specialties tended to conform to expectations, both when comparisons were made between specialties in the same service and when between comparable specialties across services. Although further research is required before conclusions can be drawn regarding efficient mixes between formal and on-the-job training, the results suggest that it is possible to draw meaningful conclusions from data based on the carefully constructed ratings of supervisors. (A number of productivity paths are presented to show the general character of the data collected.) (JT)