Emergency contraception, also called postcoital contraception, is the use of hormonal or mechanical methods to prevent pregnancy after an episode of unprotected intercourse. Although a number of methods of emergency contraception exist, its use in the United States is not widespread. This report reviews studies on the efficacy of hormonal methods of emergency contraception, as well as the literature on women's and physicians' knowledge of and attitudes toward this method of preventing pregnancy. Articles were selected for this review from a MEDLINE search using the term "postcoital contraception." These studies show that a variety of hormonal regimens are effective in reducing the chance of pregnancy when administered within 72 hours of an episode of unprotected intercourse. Failure rates range from 0%-4.66%, depending on the regimen and the study, although some controversy exists about how to calculate efficacy. Recent studies indicate that mifepristone (RU486) may be more effective than other methods, with fewer side effects. However, the more significant issue surrounding emergency contraception may be the reasons for its infrequent use in this country. A number of limitations to use have been identified in the literature, including lack of knowledge of the method among patients and physicians, inadequate counseling, and fears that widespread use of emergency contraceptives would lead to less consistent use of other methods of contraception.