Dietary phytate may bind to proteins from feed ingredients by making indigestible nutrient-complexes. Therefore, it is possible that adding exogenous phytase to the diets increases digestibility of amino acids (AA). However, results of experiments in which microbial phytase has been added to diets fed to pigs have not consistently demonstrated increased ileal digestibility of AA. It is, however, possible that is because the dose of phytase was too low to obtain a positive effect on AA digestibility and that if greater doses were used, a positive response would be obtained. Therefore, the objective of this experiment was to test the hypothesis that super dosing four different sources of commercially available exogenous phytase increases the apparent ileal digestibility (AID) of CP and AA in a corn-soybean meal (SBM) based diet fed to growing pigs.