BACKGROUND: In France, the 1999 introduction of a dedicated emergency contraceptive pill (ECP) available without a prescription has resulted in a 72% increase in its use over the past 5 years, especially among younger women. METHODS: We used a population-based health survey conducted in 1999 and in 2004 to examine the changes in the determinants of lifetime ECP use among women aged between 15 and 24 years. We also explored the determinants and circumstances of recent use of ECPs in 2004 among women aged between 15 and 44 years who are at risk for unplanned pregnancy. RESULTS: In 1999, 14.6% of women aged between 15 and 24 years had ever used ECPs; this proportion rose to 31.7% in 2004. Results show consistent patterns of lifetime ECP use in 1999 and in 2004, with greater use among higher-educated women and women living in large cities. In 2004, 22% of women were using no contraceptive at the time they used ECPs and 84% resumed use of a regular contraceptive after ECP use. However, 5.5% had unprotected intercourse after taking ECPs in the same menstrual cycle and in the next. CONCLUSION: Despite direct pharmacy access, differences in ECP use remain by social and residential status. Emergency contraceptive pills were used as a backup method in case of contraceptive failure and did not impede the use of subsequent regular contraception.