A series of studies were conducted to investigate the use of soy-based protein sources on the growth performance and body composition of juvenile largemouth bass (Micropterus nigricans). In the first trial, 50% of the fishmeal (48 g/100g diet) in the basal diet was replaced on an equal protein basis with solvent-extracted soybean meal (SBM, 34.6g/100g diet), soy protein concentrate (SPC , 22.9 g/100g diet), or enzyme-treated soybean meal (ESBM, 28.1 g/100 diet). In the second trial, nine isonitrogenous (40%) and isolipid (8%) treatment diets were evaluated. This basal diet contained 50% SBM as the primary protein source. The SBM was incrementally replaced on an isonitrogenous basis with 40%, 60%, 80% and 100% using L- SBM or E- SBM. Each aquarium was stocked with fifteen 8.55±0.18g juvenile largemouth bass and the fish were randomly assigned to the above nine treatment diets (six replicates of Basal, LSBM100% and ESBM100%; four replicates of the other six treatments). The fish were fed twice daily for six weeks. The mean weight and weight gain (g) of the fish offered the diet containing 6 0% and 80% of E- SBM were significantly higher than those of fish fed the other treatment diets. The mean weight and weight gain (g) of the fish fed with LSBM40%, LSBM60%, LSBM80%, LSBM100%, ESBM40% and ESBM100% diets were not significantly different. The fish fed with the b asal diet had significantly lower mean weight and weight gain(g) than those fish fed the other diets. No significant differences were found in weight gain (%), PER and survival between the fish fed the nine diets. Results demonstrate that L-SBM and E- SBM are two potential ingredients which could be used in juvenile northern largemouth bass diets as a primary protein source without negative effect on growth performance.