From the human cervix uteri under various conditions, structural glycoprotein was isolated which had a remarkable resemblance in its amino acid composition to other connective-tissue glycoproteins found in mammalian tissue. It was corroborated that the amount of such a structural glycoprotein increased in pregnancy, whereas collagen content was higher in the nonpregnant control. These facts suggest that the lost collagen was replaced by those structural glycoproteins in pregnantc ervix uteri. The possible significance of those structural glycoproteins on cervical dilatation is discussed.