The effects of exercise and selenium added high fat diet on edurance and serum lipid components were studied in rats. A total of 72 male Sprague-Dawley ($150{pm}35g$, body weight) were divided into trained group and untrained group and were bred for 7 weeks. Each group had 6 different dietary subgroups; namely, basal diet, 20％ shortening and 20％ soybean oil subgroup and selenium (0.01mg％) added each subgroups. Exercises of 8-min treadmill running and 10-min swimming were given to the trained group every other day during the experimental period while only treadmill running was given to the untrained group during the last week. The amounts of food intake, changes in body weight and endurance were determined once a week and serum lipid components were measured before and after experimental period. Following are the results obtained : 1) The untrained group took a slightly larger amount of food than that in the trained group. The food efficiency is, however, higher in the trained group. Body weight increased more in untrained group, while high fat diet resulted in greater increment in body weight than that in normal diet groups. 2) The trained group showed remarkably longer endurance than the untrained group and selenium added high fat diet enhanced the effect. 3) The trained group showed lower blood level of T-chol., TG and TG/PL than the untrained group. All the other blood values of HDL-chol., PL, MDL-chol./T-chol., HDL/LDL and A/G ratio were higher in trained group. 4) Soybean oil added dietary groups exibited lower blood levels of T-chol., TG, TG/PL and A/G than those in shortening added dietary groups. On the contrary, the former groups showed higher blood HDL-chol., PL., HDL, HDL-chol. and HDL/LDL ratio than those of soybean oil added dietary groups. 5) $LDH_5$ was the most abundant one among serum LDH isozymes. The electrophoretic pattern of serum LDH isozymes was not changed by exercise training and selenium added high fat diet. 6) Exercise training lowered blood GOT and TBA. These effects were enhanced by soybean oil added diets. From the above results it was concluded that a regular and long term exercise training as well as a small amount of selenium added high fat diet result in reduction of body weight and TBA and improve dietary efficiency and physical endurance in rats.