Transcutaneous electrical nerve stimulation (TENS) has been suggested as a means to reduce the amount of intravenous analgesia/sedation in patients undergoing extracorporeal shock wave lithotripsy (ESWL). A retrospective analysis of 79 ESWL procedures on 73 consecutive unselected patients was done in an attempt to determine the effectiveness of TENS in reducing the amount of intravenous fentanyl citrate and/or midazolam HCl needed to control pain and anxiety during the ESWL procedure. The study was divided into two parts: (1) all patients receiving TENS (n = 44) versus a non-TENS group (n = 35), and (2) comparison of the early (n = 22) and late non-TENS (n = 22) groups against each other; separately the late non-TENS group was compared to the entire TENS group. In the study, TENS reduce the amount of fentanyl citrate needed to control anxiety by 22.9% (P less than 0.025). No difference was noted when the early and late non-TENS group of patients were compared to each other. A gender difference was noted with a significant reduction in the dose of fentanyl citrate only in female patients receiving TENS (45.4%). Likewise, there was a significant reduction in the dose of midazolam HCl only in males who had TENS (38.9%). The data suggests that TENS may be a useful addition to reduce the amount of sedation and analgesia during ESWL.