Background: Determination of correct working length is one of the keys to success in endodontic therapy. Aim: The aim of this study was to evaluate the diagnostic efficacy of various methods to determine working length of root canal. Materials and Methods: Tactile method was assessed using digital radiography and compared with electronic method using apex locator. A total sample of 30 single rooted young permanent teeth the (mandibular first premolars) with matured apices were selected for the study. Access cavity preparation was carried out. Working length was measured by tactile method using digital radiography and electronic method using apex locator with no 15 K file. Actual working length was established by grinding of cementum and dentine from the root apex and was observed under stereomicroscope. Data was collected and statistical analysis was carried out with the help of SPSSâ15. Results: The results of this study showed that there was a significant difference between tactile method assessed by digital radiography and electronic method using apex locator. Conclusion: Apex locator was found to be more reliable and accurate when compared with the actual length.