This study was performed to investigate the effects of cardiorespiratory function on the change of serum LDH activity and distribution of isoenzyme during recovery phase after maximal and submaximal exercise with athletes and nonathletes. This results were as follow : 1. The cardiorespiratory function of athletes as maximal oxygen uptake and lactate threshold was superior to that of nonathletes. 2. The change of serum LDH activity after maximal exercise showed higher than the change of serum LDH activity after submaximal exercise, and the increase of serum LDH activity in athletes showed higher than nonathletes. 3. The changes of distribution of isoenzymes after maximal and submaximal exercise in nonathletes showed higher than athletes. In the changes of distribution of isoenzymes, the change of heart type was related to submaximal exercise, however the change of muscle type was related to maximal exercise. In this results, we think that the lower level of cardiorespiratory function were the more the change of distribution of isoenzymes and level of fatigue. In addition to, we proposed that the investigation of optimal level in exercise prescription required the analysis of detail items as the change of isoenzyme distribution.