Abstract: Twenty crossbred barrows weighing 35.8�3.1 kg, were fed 1 of 5 diets (N = 4) to determine the effects of different cereal grains on fecal P excretion and composition. The diets contained 97.15% corn, wheat, high fat-low lignin oat, normal barley or low phytate barley with the cereal grain supplying the sole source of dietary phosphorus. The diets were fed for a 7 day acclimation period followed by a three-day fecal collection. Total tract digestibility coefficients were determined for dry matter, phosphorus and phytate using the indicator method. Fecal phosphorus was characterized using solution state Phosphorus Nuclear Magnetic Resonance spectroscopy (³¹P-NMR). Water Soluble Phosphorus (WSP) and the ratio of WSP to total phosphorus (WSP:TP) were determined in the feces. Digestibility coefficients for phosphorus and phytate ranged from 0.11 (corn) to 0.46 (wheat) and 0.94 (oat) to 1.00 (corn and low-phytate barley), respectively. There was very little phytate phosphorus excreted in the feces regardless of the type of cereal grain fed (< 6% of total phosphorus) and phytate degradation was not related to the level of endogenous phytase in the diet. There was a negative relationship between the fecal WSP:TP ratio and the concentration of phosphate monoesters in the feces. In summary, our results indicate that the majority of the phosphorus in the feces of pigs fed cereal grains is present in the form of inorganic phosphate and only trace amounts of phytate are excreted intact. The amount of phytate in the excreta was not related to the amount of phytate or endogenous phytase in the grain. Further research should be conducted with diets more typical of those used in commercial swine production to confirm these findings, as the high inorganic phosphate content and WSP:TP ratio in manure from swine could increase the potential for off-site phosphorus losses when swine feces are applied on agricultural lands.