A microwave applicator was developed and tested in a rabbit model, with the goal of developing a system to sterilize a human female through a transvaginal-transcervical- transuterine retrograde technique. The clinical procedure wold create an occluding lesion in the isthmic portion of the human fallopian tube in an out-patient procedure. The microwave applicator consisted of a flexible coaxial cable from which the inner conductor was extended to form a resonant monopole antenna. The coaxial cable and monopole were placed within a sealed teflon catheter of 3 mm diameter. A second parallel catheter of 1 mm diameter was secured to the first to provide guidance for a microwave- immune thermometry probe. Following laparotomy exposure, the applicator was placed with a transvaginal-transcervical retrograde technique in each uterine horn in succession. The temperature was elevated to 65 degree(s)C for 5 minutes. Thirty days following treatment, there was marked constriction and discoloration of the treated site as well as significant architectural effacement of the tissue composing the uterine wall. In some cases, the uterine lumen was completely occluded. Future experiments will assess the tissue response to smaller thermal doses.