Postobturation pain of different origin after endodontic treatment was studied in 100 patients after treatment of 151 teeth with filling of 264 channels. 34.4% patients complained of pain. The incidence and intensity of pain were scored. Postobturation pain clearly depended on the number of treatment sessions, number of channels filled in one tooth, and excessive filling "beyond the apex". The method of "crown down" preparation using completely rotating profile instruments and GT rotary files proved to be most effective as regards prevention of postoperative pain.