Acid and neutral proteases were found in the ovarian follicular walls in the domestic fowl, and their properties were investigated.Acid protease was present mostly in the soluble fraction of the tissue homogenate in 0.01M CaCl2 containing 0.25% Triton X-100, whereas neutral protease was present mostly in the insoluble fraction. The pH optima for acid and neutral proteases were 4.0 and 7.0, respectively. Both of the captoethanol, EDTA and Ca2+. Both of the enzyme activities were affected by neither chicken serum nor soybean trypsin inhibitor.The acid protease activity (units/g of follicular wall) was significantly increased after ovulation, whereas the neutral protease activity was decreased after ovulation, followed by a subsequent increase many hours later. Jpn. J.Zootech. Sci., 52 (10) : [730][731][732][733][734][735] 1981 The presence of proteolytic enzymes such as acid and neutral proteases in the ovarian follicles has been reported in mammalian1-6) and avian species7). The enzymes are suggested to play an important role in rupture of follicles at ovulation. NAKAMURA and NAKAJO7) studied neutral protease in ovarian follicles in Japanese quails in relation to ovulation. However, little information is available on the properties and physiological roles of the proteolytic enzymes in the ovarian follicles in avian species.The present paper describes the detection and properties of acid and neutral proteases in the ovarian follicles in the domestic fowl. Changes in the activities of these enzymes, before and after ovulation, were also investigated. Materials and MethodsPreparation of ovarian follicular walls. The largest follicles and the post-ovulatory follicles (the most recently ruptured follicles) were obtained from White Leghorn laying hens killed at various hours before and after the expected ovulation of the second ovum of a 5-6 egg clutch. After each follicle was frozen on dry ice, the follicular wall was separated from the yolk Preparation of crude protease.