This study investigated effects of a Manpower Development Training Act (MDTA) program on the self-concept of 178 male adults, high school graduates and dropouts, enrolled in the Agri-Business School. The dropouts were divided into those who successfully passed General Educational Development (GED) tests and received a high school diploma (GED Successful), those who tried but failed (GED Unsuccessful), and those who did not try to obtain the diploma. Self-concept changes were examined in relation to age, intelligence, length of training, and educational accomplishment. These were the conclusions: (1) graduates and nongraduates did not differ significantly on self-concept scores as they entered the MDTA program; (2) participants did show significant self-concept changes (positively related to educational accomplishment and length of training) during their enrollment in the program; (3) intelligence seemed significantly related to change for all groups but GED Unsuccessful; (4) age seemed significant in the total group and for both GED groups. Recommendations called for additional research on the variables, flexible grouping of trainees, and more attention to motivational considerations. (Author/LY)