p94 (also called calpain 3, nCL-1, or CAPN3) is a calpain large subunit homologue, which is predominantly expressed in skeletal muscle (1 –4 ). The mRNA level of p94 in skeletal muscle is at least 10 times higher than that for the conventional calpain subunits (1 ). However, the p94 protein is not easily detectable, since p94 undergoes very rapid and extensive autolysis immediately after translation, and its half-life in vitro is less than 10 minutes (5 ). Thus, analysis of p94 at the protein level is very difficult.