The calpain system consist of calpains, a family of Ca2+ dependent cysteine proteases whose members are expressed ubiquitously or in a tissue-specific way. Calpains are heterodimeric proteins, composed of catalytic subunit of about 80 kDa organised in 4 domains and the small 30 kDa subunit organised in 2 domains. Based on the current knowledge of the catalytic properties of the calpains, it seems that calpain activity is regulated by Ca2+ concentration, calpastatin, intracellular location and subsite specificity of the calpains. Calpains participate in a variety of cellular processes including cell motility, signal transduction pathways, the cell cycle, apoptosis, long-term potentiation, pathological states in cells and postmortem proteolysis. The exact mechanisms involved in the postmortem meat tenderization process are complex and includes a large number of different enzymes. The main myofibrillar proteolysis can be attributed to calpains. The myofibrillar toughness is considered to be affected by the development of rigor-mortis and tenderization caused by calpains break-down of the contractile proteins. Based on the relevant evidence thus far obtained, factors affecting meat tenderness, although not fully understood, are in perspective to be clarified.