One medical-treatment electrode assembly includes a medical-treatment flexible electrode supported on the outer surface of a sidewall of a flexible tube which is insertable into a patient. Another assembly includes two electrodes supported on the outer surface of a flexible tube, wherein a video camera of a flexible endoscope inserted into the tube can view patient tissue between the two electrodes. An additional assembly includes apparatus for moving patient tissue into a sidewall opening of a tube which supports a medical-treatment electrode to tighten patient tissue outside the tube against the medical-treatment electrode. A method for medical treatment includes moving patient tissue into a sidewall opening of a tube which supports a medical-treatment electrode to tighten patient tissue outside the tube into substantially full contact with the medical-treatment electrode.