This report presents the results of a study undertaken to test the possibility that pre-existing attitudes could explain the previously reported association between fitness improvement and attitudes and self-confidence. Recruits from four Marine Corps basic training platoons (n=265) provided data for the study. Scores on the standard physical fitness tests showed that one platoon had substantially above average fitness improvement and another substantially below average improvement. A comparison of these two platoons on attitude and self-esteem measures showed that the high improvement platoon had more positive attitudes toward the Marine Corps and higher self-esteem. The attitudes included greater acceptance of the need for authority and discipline, greater identification with the Marine Corps, higher commitment to achieving and maintaining high levels of performance, and greater satisfaction with the Marine Corps. (JD)