We performed a multivariate analysis to determine factors associated with knowledge and willingness to use emergency contraception in a consecutive sample of 371 post-partum women from an inner-city public hospital. Women were queried about previous contraceptive use, pregnancy history including abortions and unplanned pregnancies, and demographic characteristics. Outcomes included knowledge of emergency contraception and willingness to use it. Questionnaires were conducted in person, in English or Spanish.Of 371 women, 3% had used emergency contraception, 36% had heard of it, and 7% knew the correct timing for use. Two-thirds of the population indicated a willingness to use emergency contraception in the future. Factors positively associated with knowledge included being a teenager or more than 30 years old, prior use of condoms, and history of an elective abortion. Being multiparous, monolingual Spanish-speaking, or Asian were negatively associated with knowledge. Willingness to use emergency contraception was positively associated with being multiparous and negatively associated with a higher income, moral or religious objections to the use of emergency contraception, a belief that it is unsafe or a perception that it is an abortificient. Knowledge about emergency contraception, especially correct timing, remains low. Multiparous women should receive increased education given their lack of knowledge but willingness to use emergency contraception. In order to increase the acceptability of emergency contraception, educational efforts must include accurate information about its mechanism of use and safety.