The success of an endodontic treatment depends greatly upon determination of an accurate working length. Failure to accurately determine working length may lead to either incomplete cleaning and apical leakage or apical perforation and over filling. This study was carried out to compare two methods of working length determination, radiographic and electronic apex locator. These were then compared with the actual length of the tooth. The effects of age, location of the tooth, status of the pulp and condition of the tooth were also determined.