The identification of predictive DNA markers for pork quality would allow U.S. pork producers and breeders to more quickly and efficiently select genetically superior animals for production of consistent, high quality meat. Improvement in the genetic potential of swine populations to efficiently convert feed into lean, palatable pork will provide long-term economic returns to the producer. By predicting cooked meat tenderness genetic potential, such technology could be used by packers to ensure product quality and more efficiently determine optimal use of pork. The objectives of this proposal were to identify the causative sequence variation in calpastatin that likely affects tenderness in commercial-level pig populations and to develop definitive DNA markers that are predictive of pork tenderness for use in marker assisted selection programs. Because the calpastatin gene lies under QTL for tenderness in different resource populations and markers in calpastatin are highly associated with tenderness traits, we resequenced the calpastatin gene in pigs with divergently extreme shear force values in order to identify all possible mutations that could affect tenderness. We tested these polymorphisms in our research population and samples of industry pigs for association with objective measures of tenderness. From this study we have identified 5 genetic markers that were highly associated with pork tenderness in all of the populations studied representing 2,826 pigs from 4 distinct populations. These markers should be predictive of pork tenderness in industry populations.