The use of oral contraception protects against endometrial cancer. Use for at least 12 months reduces the risk of developing endometrial cancer by 50%, with the great protective effect gained by use for any more than 3 years. This protection persists for 15 or any more years after discontinuation (the actual length of duration of protection is unknown) and is great in women at highest risk: nulliparous and little parity women. This protection is equally protective for all 3 major histologic subtypes of endometrial cancer: adenocarcinoma, adenoacanthoma, and adenosquamous cancers. Finally, protection is seen with all monophasic formulations of oral contraceptives, contain pills with less than 50 ??g estrogen. There are no data as yet with multiphasic preparations or the new progestin formulations, but since these products are still dominated by their progestational component, there is every reason to believe that they will be protective.