Changes in sexual mores have led to the need for an effective emergency postcoital contraceptive agent. To meet this need various individual steroids, either alone or in combination, have been evaluated and shown to be effective in preventing pregnancy as a result of a single, unprotected coital act. No drug has received specific marketing approval in North America for this purpose. However, in western Europe, the combination of ethinyloestradiol and levonorgestrel is marketed specifically for use as a postcoital contraceptive agent. Intrauterine copper contraceptive devices have also been shown to be effective postcoital contraceptive agents, but their applicability is confined to a specific segment of the population. Other agents are also being investigated for their postcoital contraceptive effectiveness, including prostaglandins, anti-progestins, GnRH agonists, super agonists and antagonists, and HCG antagonists. Sufficient interest exists in postcoital contraception that the World Health Organization has undertaken, through their task force dealing with postcoital, once-a-month and menses-inducing agents, to develop other postcoital drugs.Changing sexual mores have led to the need for an effective postcoital contraceptive agent. Postcoital contraception is, in theory, an emergency form of contraception designed to prevent pregnancy after a single unprotected coital exposure, not an ongoing method of fertility control. However, in South America, both levonorgestrel and quingestanol acetate have been used as continuous postcoital contraceptive agents. In terms of emergency methods, high dose estrogens alone or low dose estrogen in combination with a progestin have been used effectively. Postcoital agents are belived to exert their contraceptive effect on the implantation process either by alteration in endometrial enzymatic or metabolic activity or by some other means. Copper intrauterine devices are also under investigation as postcoital agents, but their use is not considered appropriate in young, nulliparous women with multiple sexual partners. Other methods being researched for this purpose include prostaglandins; antiprogestins; gonadotropin releasing hormone agonists, super agonists, and antagonists; and human chorionic gonadotropin antagonists.