Postcoital contraception or emergency contraception(EC), commonly known as the "morning after pills", prevents pregnancy after unprotected intercourse. A comprehensive definition of EC is as follows : "specific contraceptive methods that can be used as emergency measures to prevent pregnancy after unproteted intercourse". Both drugs and certain devices can be used for emergency contraception. The best-studied regimen(Yuzpe) consists of an ordinary combination of oral contraceptives containing ethinyl estradiol and norgestrel. Conventional clinical guidelines recommend a first dose within 72 hours after unprotected intercourse and a second dose 12 hours thereafter. These drugs are most effective when taken as soon as possible after the intercourse. The Yuzpe regimen reduced the risk of unintended pregnancy by at least 75% in clinical trials. The most common side effects of the Yuzpe method are nausea and vomiting. Levonorgestrel is the synthetic progesterone. The major benefits of levonorgestrel are the decreased side effects and greater contraceptive efficacy than Yuzpe regimen. Mifepristone (RU486) is a synthetic steroid that prevents progesterone from binding to the progesterone receptors and glucocorticoid receptors. It has been used extensively in Europe as an abortifacient and also has been used as an effective EC. Its common side effect is a delay in the onset of menses, leading to anxiety for the user. The intrauterine contraceptive device(IUCD) is the only method of emergency contraception available to women presenting beyond 72 h and within 5 days from unprotected intercourse. EC is not protective against infections such as STD(sexually transmitted diseases). There are many situations where EC is indicated, including condom rupture or slip, unplanned unprotected intercourse, incidental misuse of regular contraceptive methods, and sexual assault. Emergency contraceptive pills can prevent ovulation, but an alternative major mechanism of action is to prevent uterine implantation of the embryo at the endometrial level. A 3-week follow-up visit should be scheduled to assess the result and to counsel for regular contraception. EC provides a second chance at preventing undesired pregnancies. but it should not be used as a routine birth control method, because it is actually less effective and needs a higher dose at preventing pregnancies than most types of oral contraceptives. Widespread and appropriate use of EC will provide a promising means to reduce the incidence of unplanned pregnancy and to contribute to the women's health.