Accurate length determination is essential for adequate root canal treatment. Root canal space that has not been adequately cleaned is a potential nidus of bacteria which may lead to future periapical pathosis. On the other hand, over extended obturation material will create an inflammatory reaction that can cause pain and impede healing. (1) The two most common methods of length determination are radiographs and electronic apex locators (EALs). Radiographs are an indispensable tool that will yield much more anatomical and diagnostic information than just the length of the canal, however, in vivo studies directly comparing the accuracy of the two techniques have shown that EALs are more accurate in locating the apical foramen. (2) This is due to the apical foramen being located an unknown distance from the radiographic apex, a difference which will not always be evident on a periapical radiograph. A recent meta-analysis by Schaeffer showed that the best prognosis is obtained when the canal is adequately obturated between 0 and 2 mm from the radiographic apex, highlighting the need for accurate length determination for successful outcomes. (3) In addition to length measurement, EALs will aid in the diagnosis of perforations and resorption. (4, 5) Modern apex locators operate on a principal of relative ratios of impedance which allows them work in the presence of any common irrigating solution, and are accurate in both vital and necrotic teeth. (6,7) EALs are technique sensitive, but when used in conjunction with necessary radiographs will yield the most reliable and accurate results.