Toughness is a determinant of meat quality and a common cause of unacceptability in meat products. Although calpain proteases are believed to be involved in meat tenderisation by post mortem (PM) degradation of proteins within muscle (Sensky et al., 2001), other proteolytic systems are likely to contribute to the process (Sentandreu et al., 2002). Caspases are proteases involved in protein degradation in apoptosis and are activated early in pathological events associated with hypoxia/ischaemia, not dissimilar to the hypoxic conditions in muscle after slaughter. Caspases cleave a number of proteins which are 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, 9 and 12) which activate effector caspases (such as 3 and 7) that cleave specific substrates. Our hypothesis is that caspase activity may contribute to early post mortem proteolysis and tenderisation, similar to the calpain system. The objective of this study was to investigate the relationship between changes in caspase activity during post mortem conditioning and shear force in pork.