OBJECTIVES: Two years after emergency contraceptive pills (ECPs) were made available without prescription in France, we investigated the determinants of ECP use in a representative sample of women at risk for unintended pregnancy. STUDY DESIGN: This study is based on data collected from a population-based cohort exploring contraceptive practices and abortion (N=2863). RESULTS: Among the 706 women at risk for unintended pregnancy during the first year of follow-up (2001), only 11.1% used ECPs. Women in stable relationships or using the same contraceptive method during the year were less likely to use ECPs than other women. The study also demonstrates that detailed knowledge of ECPs increases the probability of its subsequent use. CONCLUSIONS: Given the low frequency of ECP use in cases of unintended pregnancy risk, these results suggest that information campaigns should be targeted not only at women with irregular contraceptive practices but also at women who experience errors in the use of their regular contraceptive method.