The invention provides a method and system for ablation of body structures or tissue in a sphincter, sinus or orifice such as the rectum, colon, esophagus, vagina, penis, larynx or pharynx. In one aspect of the invention, the environment surrounding the targeted ablation region can be isolated or controlled by blocking the flow of gases or liquids using an inflatable balloon positioned immediately adjacent to the tissue that is to be ablated. In a preferred embodiment, the inflatable balloon also serves to anchor the catheter in place and prevent the catheter from being expelled from the body. The inflatable balloon also insures that locally administered drug remain in the area where most needed. In a second aspect of the invention, positive pressure is used to inflate the balloon. Inflation of balloon triggers the extension of at least one curvilinear electrode into the targeted tissue. Negative pressure deflates the air sac and helps retract the curvilinear electrodes so as to allow the catheter to be removed from the body without damaging adjacent body structures. In a third aspect of the invention, the electrodes are coupled to sensors that measure properties of the target region such as temperature and impedance. Measurement of these properties permits the use of feedback technique to control delivery of the RF energy and administration of fluids for cooling and hydrating the affected tissues. In a fourth aspect of the invention, the catheter includes an optical path that can be coupled to external viewing apparatus. In this way, the position of the electrodes in the body can be determined by fluoroscopic or fiber optic techniques.