To evaluate the reliability of pelvic X- ray and transvaginal ultrasound to localize Essure microinserts (Conceptus,San Carlos, California) after successful place-ment in both fallopian tubes 3 months after placement. Design: Prospective,observational study. Setting: Gynecology departments at two teaching hospitals. Patient(s): One hundred eighty- two patients who underwent hysteroscopic sterilization by placement of Essure microinserts between August 2002 and August 2004. Intervention(s): Transvaginal ultrasound, pelvic X- ray,and hysterosalpingography (HSG) 3 months after sterilizationwith Essure. Main Outcome Measure(s): Transvaginal ultrasound confirmation of correct localization of microinserts after a 3- month follow- up. Result(s): In 150 of 182 patients, confirmation of successful bilateral placement of two microinserts(300 devices) was possible. In 9 patients it was not possible to identify both devices with ultrasound, or there was doubt about the extension of the device through the uterotubal junction. The other 291 devices were identified as being in a good position.Conclusion(s): Hysterosalpingography at the 3- month follow-up after successful placement of Essure microinserts can be replaced by transvaginal ultrasonography. A 3- month follow-up with HSG after the Essure procedure is only required after unsatisfactory placements. In those patients in whom transvaginal ultrasonography can not confirm satisfactory localization, acomplementary pelvic X- ray should be performed. To evaluate the reliability of pelvic X-ray and transvaginal ultrasound to localize Essure microinserts (Conceptus, San Carlos, California) after successful place-ment in both fallopian tubes 3 months after placement. Design: Prospective, observational study. Two teaching hospitals. Patient (s): One hundred eighty-two patients who underwent hysteroscopic sterilization by placement of Essure microinserts between August 2002 and August 2004. Intervention (s): Transvaginal ultrasound, pelvic X- ray, and hysterosalpingography (HSG) 3 months after sterilization with Essure. Main Outcome Measure (s): Transvaginal ultrasound confirmation of correct localization of microinserts after a 3- month follow-up. Result (s): In 150 of 182 patients, confirmation of successful bilateral placement of two microinserts In 9 patients it was not possible to identify both devices with ultrasound, or there was doubt about the extension of the device thro ugh the uterotubal junction. The other 291 devices were identified as being in a good position. Confc (s): Hysterosalpingography at the 3- month follow-up after successful placement of Essure microinserts can be replaced by transvaginal ultrasonography. A 3- month follow -up with HSG after the Essure procedure is only required after unsatisfactory placements. In those patients in whom transvaginal ultrasonography can not confirm satisfactory localization, acomplementary pelvic x-ray should be performed.