To evaluate the accuracy of Root ZX II electronic apex locator (EAL) for root canal working length determination in primary teeth. Forty primary maxillary incisor teeth were included in the study. Root ZX II EAL was used to determine the electronic working length (EL). The working length obtained with EAL was evaluated using digital radiography with the measuring file set to EL. The samples were categorised into three groups. Group 1 (acceptable): file tip 0-1mm short of the radiographic apex; Group 2 (short): file tip > 1mm short of the apex and Group 3 (long): file tip beyond the apex. Digital radiographic working length (RL) was derived by adjusting EL to the radiographic apex. The assigned calibrations were tabulated and statistically analysed. Group 1 included 28 out of 40 teeth indicating a clinical accuracy of 70%. Group 2 contained 10 (25%) teeth whereas group 3 had only 2 (5%) teeth. Pearson correlation coefficient statistical analysis showed a high correlation (r = +0.82; p<0.001) among the groups. Root ZX II EAL can be used as a reliable device for obtaining root canal length in primary maxillary incisor teeth.