The aim of this study was to evaluate the accuracy of the electronic apex locator Root ZX compared to the Sono Explorer Mark II Junior and Apit III in detecting root perforations. Extracted human teeth (n = 30) were perforated artificially in the middle third of the root and embedded in a box containing alginate. Detection of all perforations were carried out with K-files attached to the apex locators tested. The teeth were radiographed after each electronic measurement. The actual location of the tip of the file in relation to the external root surface and the radiographic determination of the perforations were carried out using a stereomicroscope. The mean distance of the tip of the file from the external outline of the root surface was short for all instruments and clinically acceptable (0.06-0.25 mm). There was no clinically significant difference between the morphometric measurements and the radiographic measurements. No statistical significance was found between large perforations (0.55-0.60 mm) and small perforations (0.25-0.40 mm). Under the conditions of this study, all electronic apex locators tested were acceptable clinical tools in the detection of root perforations.