The purpose of this study was to evaluate the effectiveness of a transcutanous electrical nerve stimulation unit. The effects of electronic dental anesthesia and local anesthesia for deep cavity preparations i n primary molars were compared in children aged 7 to 9 years by using the Eland Color Scale. The patients had symmetric teeth requiring Class I cavity preparation. One of the teeth was treated with electronic anesthesia and the other with local anesthesia. The tooth and method were selected randomly. Both restorations were finished at the same visit. There was no statistically significant difference between the groups in the perception of pain. Fifty-six percent of the children preferred transcutanous electrical nerve stimulation, while 36% of them preferred local anesthesia.