The removal of all pulp tissue, necrotic material and microorganisms from the root canal is essential for endodontic success. This can only be achieved if the length of the tooth and the root canal is determined with accuracy. The outcome of treatment of roots with necrotic pulps and periapical lesions is influenced significantly by the apical level of the root filling. Traditionally, the point of termination for endodontic instrumentation and obturation has been determined by taking radiographs.1 Electronic apex locators have been used clinically for over 30 years as an aid in deciding where canal preparation and obturation should terminate.2 Accurate working length determination helps to decide the extent to which the instruments are placed and worked in the root canal system and this will determine how effectively the unwanted items are removed from it. This will also limit the depth to which the canal filling may be placed.3 Correct working length determination will also affect the degree of pain and discomfort that the patient would feel following the appointment. Thus it plays an important role in determining the success of the treatment. Accepted techniques for the determination of the working length include tactile, radiographic and electronic method.4 The present study was conducted to evaluate the effect of canal curvature on accuracy of apex locator.