The purposes of this study were to (a) investigate the physiological changes produced in college men after a nine-week circuit training and jogging conditioning program, (b) analyze the effects of deconditioning periods of four, six, and eight weeks upon the physical fitness of college men, and (c) compare the developmental and retentive aspects of muscular strength, muscular endurance, circulo-respiratory endurance, and skinfold measurements. Pearson Product-Moment correlations of pre-test measures, post-test measures, differences between pre-test and post-test measures, and differences between post-test and respective retention test measures did not identify any consistent pattern of developmental or retentive relationships. The components of fitness tended to develop and deteriorate independently of each other.