The study explored relationships between aptitude test composites and final school grades in Air Force technical training for various cultural subgroups based on race, educational level, and geographical area of enlistment. Regressions of final school grade on an aptitude index were compared for the different subgroups in ten samples of technical school graduates. Results indicated that where the relationship between aptitude score and technical training performance differed for the various subgroups, the performance of Negroes and high school nongraduates was overestimated. No consistent trend in prediction error was noted for the various areas of enlistment. However, there was a general tendency for final school grades of personnel from the North and Northeast to be overpredicted, while those of men from and 17 tables and figures also appear.) (Author/LY)