Thirty-five patients had carcinoma in situ of the cervix associated with pregnancy. Seven were diagnosed within a year of abortion or delivery and 28 antepartum. Considerable variation was noted in the diagnostic and therapeutic approaches to this problem during the 20 years of this study. The significant features of this review follow: (1) no invasive cervical carcinomas were overlooked in these patients, (2) residual carcinoma in situ was found in 50% of patients upon postpartum tissue study, (3) cervical cytology was unreliable in detecting the presence of residual cellular abnormalities in the interval between conization and delivery, and delivery and tissue reevaluation, (4) conization of the cervix during pregnancy resulted in six complications in 20 patients, (5) eight fetuses were jeopardized, four fatally, as a result of the diagnostic and therapeutic management of carcinoma in situ of the cervix during pregnancy.