Emergency contraceptive pills can prevent unwanted pregnancy if taken soon after unprotected sex. Getting a prescription for emergency contraception can be difficult and time-consuming. Giving emergency contraception to women in advance could ensure that women have it on hand in case they need it. We searched for studies comparing women who got emergency contraception in advance to women who got it in standard ways. We examined whether these groups had different rates of pregnancy or sexually transmitted infections. We also studied how often and how quickly both groups used emergency contraception. Finally, we looked at whether advance provision of emergency contraception changed sexual behavior. Studies showed that the chance of pregnancy was similar regardless of whether or not women have emergency contraception on hand before unprotected sex. Women who had emergency contraception in advance were more likely to report use of the medication, and to use it sooner after sex. Having emergency contraception on hand did not change use of other kinds of contraception or change sexual behavior.