The objective was to study calpain 10 during meat tenderization. Western assays were developed and changes in calpain 10, tenderization level and desmin were determined in Longissimui (LTL) during post-mortem storage. A comparison between some characteristics of calpains 1, 2 and 10 indicated differences in the pI and sub-cellular distribution. Tenderness improved gradually during post-mortem storage and was accompanied by a decline in intact desmin level. Western analysis indicated that calpain 10 is present in sheep LTL probably as two proteins (MW 73.6 and 70.7 kDa). Post-mortem storage caused a decline in the level of the 73.6 and 70.7 kDa proteins in the sarcoplasmic fraction and a concomitant increase in these proteins in the myofibrillar fraction. Changes in the myofibrillar calpain 10 proteins were strongly correlated with the rate of tenderization. To conclude, calpain 10 proteins are present in sheep LTL and the sub-cellular distribution is dynamic during post-mortem storage.