The objective was to study the potential role of calpain 3 in postmortem myofibril breakdown and meat tenderization. We determined the temporal changes in calpain 3 protein in the ovine m. longissimus thoracis et lumborum (LTL, n=4) during post-mortem storage. Concurrently, we also determined the kinetics of tenderization level, changes in MFI, degradation of nebulin and desmin, and autolysis of calpain 1. The autolysis of calpains 1 and 3 were strongly correlated with the kinetics of tenderization and changes in MFI. The best correlation was between the appearance of the autolyzed calpains 1 and 3 and nebulin degradation. Taken together, the results indicated that calpains 1 and/ or 3 might be playing a key role in post-mortem tenderization of LTL via the proteolysis of specific muscle structural proteins such as nebulin. This is the first report that relates calpain 3 to myofibrillar protein degradation in post-mortem skeletal muscle.