Access openings and lateral root perforations were prepared in 40 single-rooted extracted teeth. The distance to the perforations was measured visually and then with the Tri Auto ZX. The electronic device was used first in its apex-locating function and then in conjunction with its automatic reverse mechanism. On average, the electronically measured length was slightly shorter than the visually measured length (P < 0.05). When the automatic reverse mechanism was used, the values registered were either consistent with or slightly different (+/- 0.5 mm) from the electronically measured length (P > 0.05). The results of this study revealed that the Tri Auto ZX detected and measured endodontic root perforations within a range of clinically acceptable variations.