A study of 68 pregnant patients with suspicious or positive cervicovaginal cytologic findings revealed 20 to have carcinoma in situ and 6 to have invasive squamous-cell carcinoma of the cervix. Diagnostic studies, including punch biopsy of the cervix at any period during pregnancy and cervical conization prior to week 30 of gestation, were attended by no higher morbidity or hazard than such procedures performed in the postpartum period. In view of the hazard to both mother and fetus of the traditional cone biopsy after week 30, substitution of multiple punch biopsies or shallow ring biopsy of the cervix is recommended during the last 10 weeks of gestation. Punch biopsy of the cervix alone during pregnancy failed to detect the most serious lesion present in 25% of instances. Conization of the cervix during pregnancy is not a reliable therapeutic procedure. Residual carcinoma was encountered in 50% of uteri subsequently removed. Cytologic screening of the cervix during pregnancy is an essential feature of good prenatal care.