The studies were carried out to investigate the changes in the activities of glucose, ALT, ALP, GGT, cholesterol, $T_3$, and cortisol among the serum when the dogs were administered the prednisolone acetate. The experiments were designed to 3 groups and twenty-four dogs were randomly assigned to 3 groups of 8 dogs each. In groups I, each dog was injected 1mg of prednisolone acetate/kg/day for 14 days, intramuscularly. In groups II, 10mg of prednisolone acetate/kg/day for 14 days. And in the control group, 0.1ml of saline daily for 14 days. The results were summarized as follows: 1. In group I, II and control, mean serum glucose activities remained in the normal range during the study. 2. In group I, mean serum alanine aminotransferase(ALT) activities slowly increased until day 3, than reached the maximum(317IU/l) until day 21, and then decreased in 32.3IU/l until day 40(p<0.005). In group II, reached the maximum(184IU/l) until day 3, and gradually decreased in 140IU/l until day 54(p<0.001). 3. In group I, mean serum alkaline phosphatase(ALP) activities reached the maximum (786IU/l) until day 12 and gradually decreased in 153IU/l until day 47(p<0.001). In group II, reached the maximum(381IU/l) until day 24 and rapidly decreased in the range of control until day 33. 4. In group I, mean serum GGT activities reached the maximum(29.3IU/l) until day 12, and slowly decreased in the range of control until day 47(p<0.005). In group II, reached the maximun(102IU/l) until day 54(p<0.005). 5. Mean serum cholesterol activities of group I decreased than those of control(p<0.05). In group II, decreased than those of control(p<0.05). 6. In group I, mean serum $T_3$ activities reached the maximum(32.8ng/dl) until day 12 and increased in the range of control until day 21(p<0.05). In group II, gradually decreased in 25.1ng/dl until day 12, then decreased under the level of 25ng/dl from day 15 to day 40, and then gradually increased but remained under the range of control(p<0.001). 7. In group I, mean serum cortisol activities slowly decreased and reached the minimum($0.4{\mu}g/dl$) until day 18(p<0.001), and then increased in the range of control until day 47. In group II, rapidly increased and reached the maximum($22.1{\mu}g/dl$) until day 12(p<0.05), but decreased to the minimum($0.64{\mu}g/dl$) until day 40, and then increased in the range of control until day 47.