A 2-week experiment was conducted to detect antigenic soy proteins in plasma of pigsfed soybean meal (SBM) and fermented soybean meal (FSBM). The suitability of a com-mercial FSBM to replace SBM in diets for newly weaned pig was also evaluated. A total of 160 pigs were randomly assigned to 5 dietary treatments (n=8): 400g/kg soybean meal(FSBM-0), its replacement by protein from fermented soybean meal as 1/3 (FSBM-1), 2/3(FSBM-2), 3/3 (FSBM-3), and no soy protein in diet (PCON).