Twelve enzymatic activities, involved in the metabolism of proteins, collagen, glycosaminoglycans, or in the energy metabolism, were studied in 72 cervical biopsies obtained after delivery of the placenta and in 12 cervices obtained by hysterectomy in nonpregnant patients. Although these activities display high interindividual variations, they are greatly and significantly increased at parturition as compared to the nonpregnant state, with the exception of creatine kinase, which is maximum in cervices obtained from nulliparous nonpregnant women. The activities are low in the group of women who are 35 to 40 years old. The other studied factors (blood group, parity, pregnancy duration, labor length, treatment, state of the cervix at the 9-month examination) have no clear influence on the enzymatic levels. The results are discussed in relation to the well-known structural changes of the cervix at parturition.