Whey, which is a co-product from dairy processing plants that extract fat and protein from milk to make cheese has been used in diets fed to weanling pigs as a source of lactose. Whey powder does not contain much protein because the majority of the milk protein ends up in the cheese during processing. However, cheese co-products, which contain 40 to 50% crude protein may be used in the feeding of pigs but there is limited information about the nutritional value of cheese co-products fed to pigs. Therefore, it was the objective of this experiment to measure the apparent ileal digestibility (AID) and the standardized ileal digestibility (SID) of amino acids (AA) by weanling pigs in a cheese co-product and compare values to those obtained in fish meal and in a source of enzyme treated soybean meal (HP 300).