Abstract: The specific enzymatic generation of an "s1-casein-exorphin from milk casein was achieved by using the Staphylococcus Aureus strain V8 protease. The kinetic of proteolysis of the substrate was studied with the free and the immobilized form of the enzyme. The continuous process with the immobilized enzyme appeared highly effective for the purpose in term of yield, giving the maximal rate of bioactive peptide which could be expected. The hydrolysate was partially purified and tested for its opioid potency in the rat vas deferens bioassay system.