PIP: Each year, about 25,000 new cases of ovarian cancer are diagnosed in the US. Because ovarian cancer has few symptoms in its early stages and there is no effective screening test, most patients have widespread metastases at diagnosis. Epidemiologic studies have demonstrated that OC use can protect against ovarian cancer for at least 15 years after pill use is discontinued. The most likely mechanism of this protective effect is inhibition of ovulation. A strong association between total number of lifetime ovulations and mutation of the p53 gene in ovarian cancers has been reported. Use of the pill for 5 years decreases the risk of ovarian cancer by 40% but decreases lifetime ovulations by only about 15%, suggesting that factors other than prevention of proliferation-associated mutations contribute to the protective effect of ovulation inhibition. The pill also decreases the incidence of endometrial cancer by about 50%. At present, OCs represent the best option for US women from both the contraceptive and cancer prevention perspectives.