Calcium dependent proteolysis was examined in supernatant prepared from cultured bovine lens epithelial (BLE) cells. The presence of the calcium activated protease, calpain, was indicated by immunorecognition of 80 kDa and 30 kDa subunits of calpain in BLE cell supernatant. Degradation of125I-alpha-crystallin and FTTC labeled casein by BLE cell supernatant were shown to be calcium dependent. Inhibition of activity was achieved with EGTA, calpastatin or CbzValPheH. The data presented are the first measurement of calpain activity in cultured lens cells.