Emergency contraceptives are methods that prevent pregnancy when used shortly after unprotected sex. Three different emergency contraceptive methods are safe, simple, and widely available in the United States. These are: (1) ordinary combined oral contraceptives containing ethinyl estradiol and levonorgestrel taken in a higher dose for a short period of time and started within a few days after unprotected intercourse; (2) levonorgestrel-only tablets used similarly; and (3) copper-bearing intrauterine devices inserted within approximately 1 week after unprotected intercourse. Emergency contraceptive use is best known for women who have been raped, but the methods are also appropriate for women who have experienced condom breaks, women who did not use any method because they were not planning on having sex, or women who had unprotected intercourse for any other reason. Unfortunately, few women know about emergency contraceptives, and few clinicians think to inform their patients routinely about the option. A nationwide toll-free hotline (1-888-NOT-2-LATE) and a website (http://not-2-late.com) can help women learn about these options. Sharing "family planning's best-kept secret" widely with women could prevent as many as a million unwanted pregnancies annually in the United States.