Twenty steers and 20 bulls averaging 7 Mo. of age were employed to investigate the effects of casrration on the carcass characteristics, serum metabolites and hormones of Korean cattle from 7 Mo. to 25 Mo. of age. Dressing percent(P$lt;0.05), cold carcass weight(P$lt;0.01) and longissimus dorsi area(P$lt;0.01) of bulls and steers were 57.6±0.44; 58.6±0.36%, 306.9±0.97; 344.9±0.51Kg and 74.3±0.97; 84.7±0.15㎠, respectively. Steers had more marbling score than bulls(4.4±0.11 vs 1.5±0.22; P$lt;0.01). Differences between bulls and steers in serum insulin-like growth factor-1(IGF-1) concentrations and testosterone, stimulate protein synthesis and growth, were large(P$lt;0.01) after 15 Mo. and 9 Mo. of age, respectively. Serum cortisol concentrations had increased rapidly at 19 Mo. of age both in bulls and steers. Steers had higher cortisol concentrations, stimulate lipid metabolism and deposit of intermuscular lipid, than bulls. These results suggested that castration would be extended after 15 Mo. of age to increase beef quality and to conpensate the loss of weight gain due to castration.