Elastase activity of 294 samples of endocervical mucus taken from 125 normal pregnant women during the visits to antenatal clinic were measured. Activity of the enzyme increased gradually with the advance of gestational age. Steep rising of the enzyme was seen between 34-35 weeks of gestation and the peak was achieved at 37 week since then the enzyme activity sustained at relatively high level until deliveries. Average activity of the enzyme after 34 weeks of gestation showed significant difference over that of earlier period. To use delivery date as a referent point, the peak was reached in the last fourth week of pregnancies and then sustained until deliveries. Significantly higher average activity was also seen in these last 4 weeks of gestation. These correlated very well to the fact that cervical maturation progresses most rapidly during last month of pregnancy. Immunohistochemical staining for elastase demonstrated elastase-containing granules in polymorphonuclear leukocytes. These cells found in cervical tissue taken from immediately postpartal women were much more than in those of early pregnant women. These findings may be the evidences support roles of granulocyte elastase in the process of cervical maturation preceding spontaneous labors in normal pregnancies.