an apparatus and method for causing necrosis of tissue and specifically intended for thermal ablation of the uterine cavity to cauterizing the endometrial tissue . the apparatus includes a liquid - tight , liquid filled system having a distal flexible member ; a proximal flexible member ; and a catheter joining and providing a liquid path between these distal and proximal members . the apparatus further includes a pressurizable pneumatic chamber into which the proximal flexible member is inserted and a means to controllably heat the contents of the pneumatic chamber . the system operates to : first withdraw substantially all of the liquid into the proximal flexible member contained within the pressurizable pneumatic chamber ; second to heat this liquid to a temperature such that it can cause tissue necrosis ; and third to force the heated liquid from the proximal flexible member into the distal flexible member where it is maintained for a predetermined time and at a predetermined pressure . where this distal member has been inserted into a uterine cavity or is otherwise is in contact with living tissue , the presence of the heated liquid results in tissue necrosis and cauterization .