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The accuracy of three electronic apex locators (EALs) (Justy II, Root ZX, and Neosono Ultima EZ) is evaluated, together with the concordance of the measurements obtained by two different operators. Twenty single-root human teeth were used, sectioning the crown to gain access to the root canal. A first operator (A) determined the reference (or control) length (corresponding to the actual length) for each tooth, after which all teeth were measured individually and independently by the other two operators (B and C). The results obtained with each EAL and by each operator were in turn compared with the corresponding control length. The statistical analysis of the results showed EAL reliability in detecting the apex to vary from 80% to 85% and 85% to 90% (depending on the operator) for the Justy II and Neosono systems, respectively, whereas reliability was found to be 85% for the Root ZX device. These results, combined with a high interobserver concordance, suggest electronic root canal measurement to be an objective and acceptably reproducible technique.