Large epidemiologic studies conducted to date in the United States and abroad have not demonstrated any statistically significant increase in the overall incidence of breast cancer among women who used oral contraceptives (OCs). The cumulative risk of breast cancer among women less than 60 years of age is clearly not related to OC use, although the incidence of breast cancer in certain subgroups of premenopausal women who used OCs may be increased and warrants monitoring. Evidence of a latency period in the development of breast cancer among OC users is not convincing. Studies to date have indicated that the risk of invasive cervical cancer appears to be unaffected by OC use. The data on cervical intraepithelial neoplasia are inconclusive and fraught with confounding variables. There is unequivocal evidence that OC use reduces the incidence of other reproductive system cancers, notably ovarian and endometrial.