-A study involving 48 beef carcasses was conducted in order to evaluate the effects of 0.3 M calcium chloride (CaCl 2 ) injection on final tenderness in muscle Longissimus thoracis et lumborum. Injection of beef carcasses with CaCl 2 accelerated post mortem tenderization process. Ca 2+ -dependent proteases (µ-calpain and m-calpain) and their inhibitor (calpastatin) activities were all significantly (P < 0.01) decreased in CaCl 2 injected animals (n = 24) compared with control animals (n = 24). Tenderness, assessed by measuring shear force, was significantly improved (P < 0.05) by CaCl 2 injection both at two and eight days post mortem.