The potential association between the use of oral contraceptives (OCs) and certain types of cancer remains an important concern. Epidemiologic studies published over the past decade indicate that the overall risk of breast cancer is not increased among women exposed to OCs. Some studies have suggested an increased risk among younger women with long-term use, and this issue requires further study. OCs confer significant protection against endometrial and ovarian cancers, and the effect is duration-related: longer use is more protective. In the largest study to date, the protection against these two types of cancer persisted for at least 15 years after OCs were discontinued. Several studies have linked long-term OC use with an increased risk of cervical cancer or its precursors, but methodologic difficulties in studying cervical cancer are such that the potential association with OC use may never be clarified. A large international study has found no association between OC use for any duration and liver cancer. Neither malignant melanoma nor pituitary adenoma appears to be linked to OC use. In summary, OCs protect against endometrial and ovarian cancers and have no overall effect on the risk of breast cancer. Women using OCs should have regular Papanicolaou screening.