The objective of the present work was to characterize changes in calpain activity in pork post-mortem. Samples from pig M. longissimus dorsi and M. semimembranosus were collected three days post-mortem from 75 animals and analyzed with casein zymography. The results indicated post-mortem autolysis of m-calpain as two m-calpain bands were observed on the zymogram gel. Use of M. longissimus dorsi from three pigs collected at different times during storage further confirmed post-mortem autolysis of m-calpain. The activity of the autolyzed form of m-calpain was detectable at day 3 and further increased at day 6. The results also showed a decrease in the non-autolyzed m-calpain activity during post-mortem storage. Collectively, these results suggest that m-calpain is active post-mortem in porcine muscles.