Background and study aim:This study was designed to asses the usefulness of colonovideoscope with variable stiffness, compared with conventional videoscopes. Patients and Methods:The first prototype XCF-QAY1 and the latter prototype XCF-Q240AI used in this study can be varied to 4 stages of stiffness modes of tube insertion during examination. (1) floppy mode is the same stiffness of PCF, (2)normal mode is the same stiffness of conventional videoscopes, (3) half of stiffness between 2 and 4, (4) stiff mode is same stiffness of CF-200HI that is a little flexible than sliding tube. We especially made attention that variable stiffness could be used only after colonoscope straightend and not be used during loop formation. In the 352 consecutive colonoscopy examinations perfomed using these scopes, the following data were recorded: the time for intubation to the cecum, frequency of change in the patient's posture, frequency of abdominal manipulation attempt, pain score and patient profiles(age, sex, past abdominal and pelvic surgical history, obesity). The mode of the stiffness of the insertion tube and the examiner's impression score were recorded only in cases using the above mentioned scopes. Results:There was no significant difference among each colonoscope case in the pain score. Total colonoscopy rate was 97.4%. The frequency of varying stiffness sites in the colon as follows:descending colon(56.8%), transverse colon (33.3%), sigmoid colon (7.6%) and ascending colon(2.3%). A significant difference in the mean time for intubation to the cecum between XCF-Q240AI and conventional scopes was observed. Moreover, there were significant differences in the time of abdominal manipulation attempt and change in the patient's posture between conventional scopes and the new scopes. Conclusions:These results suggest that only one scope, especially XCFQ240AI is needed for any colonic examination by any examiner.