OBJECTIVE: The contraceptive efficacy of intrauterine devices (IUD) is thought to relate to the position of the IUD in the uterine cavity. Several trials examined the number of copper IUD expulsions, but none evaluated the partial and complete expulsion rate of the levonorgestrel-releasing device (LNG-IUD). STUDY DESIGN: This retrospective cohort study compares the dislocation rate of the Multiload 375 IUD (ML 375) and the LNG-IUD in 214 women (107 subjects with each IUD). Transvaginal ultrasound was used to monitor the IUD position immediately after insertion, after 6 weeks, and later on at intervals of 6 months. The observation period included 3631 cycles. RESULTS: We detected a significantly lower number of dislocations in LNG-IUD users. Previous expulsion was associated with a significantly higher risk for a re-expulsion in both IUD groups. Hypermenorrhea was not associated with an increased dislocation rate in LNG-IUD users. CONCLUSION: Expulsions are less likely to occur with the LNG-IUD, which might contribute to its contraceptive efficacy.