Objective To identify the determinant of the occurrence of IUD expulsionMaterials & Methods Based on 25 733 IUD uses from the Chinese Two-per-Thou-sand Fertility Survey data, this study examines the patterns and differentials of IUDexpulsion rate by characteristics of women, and identifies the socio-demographic deter-minants of IUD expulsion. A Life Table method was used to calculate the cumulativeexpulsion rate and a random-effects discrete-time survival model was employed to as-sess the impact of potential determinants simultaneously on the risk of expelling anIUD.Results Three major findings are observed in this study. First, IUD expulsion wasthe second main reason, after pregnancy during IUD use, for IUD discontinuationduring the first four years of IUD insertion; the expulsion rates were 6. 4%, 9. 1%,10. 8 %, and 12. 0% at 12, 24, 36and 48months, respectively. Second, there was aclustering of IUD expulsion: some women experienced repeated IUD expulsions.Third, some socio-demographic characteristics and fertility history were associatedwith the occurrence of IUD expulsion. In particular, the expulsion rate was highamong young women, among those with two or more children and among those livingin rural areas.Conclusion The above mentioned factors shoald be addressed in order to decrease theIUD expulsion rate and enhance the reprocluctive he alth of women.