Incarceration affords an opportunity to provide health care to populations with limited access to care. Women in this population are at high risk for experiencing unintended pregnancies. It is not known what proportion of these women engage in unprotected intercourse in the days prior to incarceration and therefore may benefit from being offered emergency contraception upon their arrest to decrease their risk of unintended pregnancies. We sought to describe the proportion and characteristics of newly arrested women who are eligible for and interested in taking emergency contraception by conducting a cross-sectional study in an urban county jail booking facility. A 63-item survey was administered to women ages 18-44 within 24 h of being arrested in San Francisco. Eighty-four (29%) women were eligible for emergency contraception. Of these, 48% indicated a willingness to take emergency contraception if offered. Half of the women eligible for emergency contraception expressed ambivalent attitudes about pregnancy. Women who had taken emergency contraception in the past were more likely to say they would accept it (45%) than women who had never used it (25%, p = .05). The strongest predictor of willingness to take emergency contraception was not having a misperception about its safety, efficacy, or mechanism of action (RR = 1.9, 95% CI 1.2-3.0). Seventy-one percent of all women indicated that they would accept an advance supply of emergency contraception upon release from jail. Emergency contraception counseling and provision should be offered to newly arrested women as a key reproductive and public health intervention for a traditionally marginalized, high-risk population.