The purpose of the present study is to investigate the effects of prolonged exercise training on antioxidant enzymes in genetically hypercholesterolemic strain of rats(RICO). Thirty five(six weeks old) genetically hypercholesterolemic strains of male rats served as subjects in the experiments. They were divided into five groups: seven control resting (CR), seven control exercise (CE), seven control aged (CA), and seven trained resting (TR), and seven training aged exercise (TAE). TR and TAE groups of the present study participated in a regular training program five times per week for nine weeks, whereas CR, CE, and CA groups did not participate in the training program. Blood sampling were taken at the laboratory of the Department of Laboratory Animal Medicine, Yonsei Medical Research Center and were analyzed for antioxidant enzymes(SOD, GPx, and CAT). The conclusions obtained from this study were as follows; In the SOD levels, there was a significant difference after regular training program between CA and TR groups and also a significant difference between CE and TAE groups(p<0.0001). The GPx levels were significantly different after a regular training program, whereas CE and TAE groups were slightly decreased after highly intensive exercises. The CAT levels were highly increased after aging and regular training programs, however, there was no significant difference between CA and TR groups and they were significantly increased after highly intensive exercise in the TAE. However, they were slightly increased after highly intensive exercise in the CE(p<0.0001). In this study, we can conclude that regular exercise training improves antioxidant enzymes in genetically hypercholesterolemic strain of rats. Therefore, we can trace the effects as direct results of the aerobic training. Additional factors such as nonenzymatic antioxidants include vitamin C & E, β-carotene, and GSH(glutathione) might be considered in order to evaluate the intact relationships between immune system and antioxidant system in genetically hypercholesterolemic strain of rats.