Epidemiologic data on the use of oral contraceptives and estrogen replacement therapy in relation to cancers of the endometrium, breast, and ovary are briefly reviewed. This is followed by a more detailed review of the epidemiologic literature on hepatic adenomas and primary hepatocellular carcinoma. There is evidence that combined oral contraceptive use increases the risk of hepatocellular carcinoma in developed countries in which rates for this disease are extremely low. Any such elevation is, however, as yet undetectable in countries where hepatitis B virus is endemic and liver cancer rates are high.