Soybean meal (SBM) is a source of P in diets for swine. However, the P in SBM is stored as part of phytate, and pigs have very limited production of endogenous phytase. Therefore, to improve P availability, commercial pig diets often include supplemental phytase. This practice increases P digestibility, decreases the need for added phosphate, reduces feed costs, and decreases phosphorus excretion in manure. The release of P from phytate in SBM is believed to be in a dose-response manor. In addition, the destruction of phytate that is caused by phytase will also result in release of inositol, which is a sugar that may improve growth performance of pigs. However, there is very limited knowledge about how different levels of phytase influence plasma concentrations of inositol in growing pigs. Therefore, the objective of this work was to test the hypothesis that inclusion of microbial phytase in diets for growing pigs containing SBM will improve the digestibility of P in a dose-response manner and that inclusion of microbial phytase in diets for growing pigs also will increase plasma inositol levels of pigs.