This study was carried out to evaluate the change of blood constituents during the growth of antlers in Korean spotted deer (Cervus nippon). Samples of blood, obtained from the jugular vein of twenty five deer (3 to 6 year-old males) were taken in 10 days interval from casting to cutting of antler and were analyzed the blood parameters. Total-protein concentration in blood serum showed significantly differences during growth period of velvet antler (p<0.01), and it had similar tendency for total protein and albumin concentration, but albumin concentration was about 40-45% of total protein concentration. Urea and creatinine concentration was tended to inverse proportion, and it was almost 30:1 for ratio of urea and creatinine concentration. The concentration of total protein, creatinine, and uric acid concentration in blood during growth period of velvet antler was similarly increased and decreased but urea concentration was opposed. The concentration of total-bilirubin and direct-bilirubin at casting was higher than those at other period(P<0.05).