Fifty-five men between the ages of 17 and 59 participated voluntarily in a 10-week program of jogging. The group was randomly divided into two subgroups, one training 12 minutes/day, 3 days/week; and the other training 24 minutes/day, 3 days/week. Both groups demonstrated significant increases in vital capacity, Max VO2, and O2 pulse; and significant decreases in both resting systolic and diastolic blood pressures, resting heart rate, and maximal heart rate. A decrease in residual lung volume was found only in the 12 minute group while only the 24 minute group showed significant decreases in weight and increases in total work, maximum tidal volume and Max VE. While the 24 minute group generally demonstrated changes in the desired direction of greater magnitude, the differences between these two groups relative to their respective changes were not statistically significant, with the exception of the residual volume. In addition, age did not appear to influence the degree of physiological change resulting from this training program.