Abstract. Meat tenderness is an important trait in beef cattle production, as consumers consider tenderness the most important attribute of beef palatability. There is ample evidence that post mortem proteolysis of myofibrillar proteins is responsible for the decline in shear force during storage. The bovine micromolar calcium-activated neutral protease (CAPN1) gene encodes the large subunit of μ-calpain, which is thought to be one of the most important enzymes involved in post mortem tenderization (KOOHMARAIE 1996). Three single-nucleotide polymorphisms (SNPs) on the CAPN1 gene (316, 530 and 4 751 markers) have been associated with tenderness in different cattle breeds (PAGE et al. 2002, PAGE et al. 2004, WHITE et al. 2005). A more recent study confirmed that markers 316 and 4 751 had an effect on beef tenderness (VAN EENENNAAM et al. 2007). The objective of this research was to determine the existence of polymorphisms and to assess the effect of the reported SNP in the bovine CAPN1 gene on tenderness from a sample of Angus and Brangus steers fattened on pasture.