OBJECTIVE: To review the pharmacology, pharmacokinetics, efficacy, and safety of data of ulipristal acetate, a new emergency contraceptive approved for use up to 120 hours after unprotected intercourse. DATA SOURCES: Articles pertaining to the topic were identified and reviewed through searches of PubMed (1994-March 2011) and clinicaltrials.gov , using the key terms ulipristal and CDB-2914. Ella approval documents were obtained and reviewed from Drugs@FDA on the Food and Drug Administration (FDA) Web site. STUDY SELECTION AND DATA EXTRACTION: All published data and FDA approval documents examining pharmacologic, pharmacokinetic, and clinical studies related to ulipristal acetate as an emergency contraceptive were evaluated. Selected studies included 3 randomized trials and 1 meta-analysis. DATA SYNTHESIS: Ulipristal acetate is a progesterone agonist/antagonist emergency contraceptive approved for the prevention of pregnancy to be taken as soon as possible, within 120 hours after unprotected intercourse or a known or suspected contraceptive failure. Based upon results of the Phase 3 clinical trials used to obtain approval, ulipristal acetate administration was at least as effective as levonorgestrel in the reduction of pregnancy rate when studied alone after unprotected intercourse and when taken up to 120 hours after unprotected intercourse. Commonly reported adverse effects associated with ulipristal acetate in trials included headache, breast tenderness, nausea, and abdominal pain. CONCLUSIONS: Ulipristal acetate is effective as an emergency contraceptive for up to 120 hours after unprotected intercourse. Because ulipristal is available only via prescription, it may be covered by insurance. However, the additional factors of travel expenses and time to make and attend a physician appointment must be taken into account when considering use of ulipristal as an emergency contraceptive. Due to the similarity of its structure to mifepristone, controversy regarding ulipristal's mechanism of action has arisen.