Toughness is a determinant of meat quality and a common cause of unacceptability in meat products. Calpain proteases are believed to be involved in meat tenderisation by post mortem degradation of myofibrillar proteins (Sensky et al., 2001). However other proteases are likely to contribute to the proteolysis involved in meat-conditioning (Sentandreu et al., 2002). Caspases are proteases involved in protein degradation in apoptosis. Like calpains caspases are activated early in pathological events associated with hypoxia/ischaemia, which is not dissimilar to the hypoxic conditions in muscle after slaughter. Caspases specifically cleave a number of proteins that are also targeted by calpains during post mortem proteolysis and also degrade the calpain-specific inhibitor calpastatin. The caspase system has a hierarchy of initiating isoforms (such as caspases 8 and 12) which activate effector caspases (such as 3 and 7) that cleave specific substrates. Caspases are regulated by inhibitors such as apoptosis repressor with caspase recruitment domain (ARC). Our hypothesis is that caspase activity may contribute to early post mortem proteolysis and tenderisation, similar to the calpain system. The aim of this study was to characterise the caspase system in various porcine skeletal muscles.