Half of all pregnancies in the USA are unintended, suggesting a high incidence of either improper or nonuse of contraceptives. Emergency birth control (EBC) provides individuals with additional insurance against unplanned pregnancy in the presence of contraception failure. This study is the first to estimate the impact of switching EBC from prescription to nonprescription status in the USA on abortions and risky sexual behavior as measured by STD rates. Utilizing state-level variation in access to EBC, we find that providing individuals with over-the-counter access to EBC leads to increase STD rates and has no effect on abortion rates. Moreover, individual-level analysis using the National Longitudinal Survey of Youth indicates that risky sexual behavior such as engaging in unprotected sex and number of sexual encounters increases as a result of over-the-counter access to EBC, which is consistent with the state-level STD findings. Copyright (c) 2015John Wiley & Sons, Ltd.