Describes some early results of research designed to evaluate the economic efficiency of specialty training for first-term enlisted personnel. To make such an evaluation, one must develop reliable measures of on-the-job performance that (1) reflect net rather than gross productivity, (2) reflect productivity over time, and (3) are based on the performance of specific individuals. Measures that have these properties can be collected by a variety of methods, including direct measurement, job-knowledge tests, and supervisory ratings. The authors provide a preliminary analysis of supervisory rating data assembled to explore tradeoffs among training courses of different lengths. These data consist of enlisted supervisors' estimates of military trainee net productivity at different points in first-term service. The estimates are used to construct profiles of the time path of productivity; a number of profiles are presented. Results suggest that meaningful conclusions can be drawn from data based on carefully constructed supervisory ratings.