The effect of methionine supplementation to the isolated soyprotein(ISP) diet on the growth, body metabolism and composition of the Albino male rats was studied. Three levels(0.3,0.6 and 0.9%) of methionine were supplemented to the ISP diet with the constant levels of energy and protein of 3,600 kcal/kg and 20%, respectively. The body weight and weight gain of the growing rats were significantly increased by 0.3% methionine supplementation to the ISP diet compared to the ISP diet(P< 0.05).The effects of methionine supplementation to the ISP diet tended to be larger with increasing of the level of methionine supplementation, 0.6 and 0.9%, were statistically insignificant. Food and gross energy intake of growing rats fed the ISP diet or the ISP supplemented with methionine diet were lower than those fed the casein diet(P< 0.05). FER and PER of all the methionine supplemented diets were higher than those of the ISP or casein diet (P< 0.05) without significant differences among the supplementation levels of methionine to the diets. The weight gain of adult rats fed 0.9% methionine supplemented ISP diet were higher than those of the other treatments with significant difference. The effects of methionine supplementation to the ISP diet on the protein digestibility, BV, NPU, N-balance, N-retention, and body and liver compositions were not significant.