Gastric proteases from seal stomach were isolated following homogenization, extraction, centrifugation and ammonium sulfate precipitation/fractionation. The crude seal gastric proteases (SGP) were stable in acid conditions with optimum stability at pH 3 0, but were unstable in the alkaline range. The crude SGP possessed excellent temperature adaptability with relative activities of 70 and 90% at 5 and 25°C, respectively. The activity of crude SGPs was retained up to about 40 min incubation at 70°C. The isolated SGP were immobilized on glutaraldehyde-treated chitin. The immobilized SGP exhibited optimum performance at pH 2 0, were most stable at pH 4 0 and had a 90 h half-life in a column with continuous operation for haemoglobin hydrolysis at room temperature. The native SGP clotted milk rapidly at pH 5 8 to 6 6; however, immobilized SGP had a lower milk-clotting activity.