Apparatuses and methods are disclosed for introducing a conductive fluid and delivering an electrical current to the fluid at a target site in a body lumen. The electrical current is delivered to the site by a conductive electrode through the conductive fluid, causing the tissues in the lumen walls, or peripheral to the lumen walls, to heat and contract. Application of the current can be discontinued when the lumen wall has contracted or been reduced to the desired extent, which will often be complete occlusion. Alternatively, the current can be applied until tissues peripheral to the lumen are effected.