Transcutaneous nerve stimulation (TNS) applied both ipsilaterally and contralaterally with a tonic pain stimulus was compared to a control condition to determine its effect on pain reports. The ipsilateral TNS condition significantly reduced ratings and increased pain thresholds relative to the contralateral and control conditions which did not significantly differ from each other. A Signal Detection Theory analysis of the data was employed to assess the sensitivity and response bias effects of the treatment conditions. Ipsilateral TNS significantly reduced pain sensitivity and response bias in the direction of showing a lesser tendency to report pain. The effects of ipsilateral TNS were most pronounced at the higher levels of stimulation. The results are consistent with Gate Control Theory which holds that ipsilateral TNS attenuates painful sensation. Most importantly, these results support the efficacy of TNS for the treatment of clinical pain.