Test procedures were developed for measuring the residual milk clotting activity of a protease produced by Endothia parasitica in curd and viii whey separated from freshly coagulated milk. A substrate was prepared by reconstituting 6 g low heat nonfat dry milk in 500 ml buffer containing 50 ml 0.5M cacodylic acid, 50 ml 0.2M CaCl2 , 30 ml 0.2M triethanolamine and 370 ml double distilled water. The substrate was stored at 2 to 4 C for 20 hours before use. Two milliliters of whey or supernatant from centrifuged curd-water slurries were inoculated into 25 ml of substrate at 30 C and the coagulation time noted, and compared with that produced by a known dilution of a standard enzyme solution. Endothia parasitica curd formed at pH 6.7 contained 45 per cent of the enzyme activity added to 454 g milk hut when formed at pH 5.2 the curd contained only 25 per cent. ix The recovery of Endothia parasitica protease in curd was made by preparing a 1:5 curd-water slurry, adjusting to pH 5.4, filtering and testing the filterate.