Rye contains considerable quantities of intrinsic phytase and the presence of phytase in rye may result in an increased P digestibility in pigs without using exogenous phytase. It is possible that the endogenous phytase in rye also increases P digestibility in other plant feed ingredients by releasing P from the phytate. However, to our knowledge, no data demonstrating this effect have been published. Therefore, the objective of this experiment was to test the hypothesis that inclusion of rye in diets containing corn and soybean meal (SBM) without or with microbial phytase improves the apparent total tract digestibility (ATTD) of P and Ca and thus the ATTD of P is not additive in the mixed diet.