This controlled trial examined the benefit of a high-frequency transcutaneous electrical nerve stimulation (hfTENS) device (Quell ) for chronic low back pain (CLBP) patients. Thirty-five (N=35) participants were randomly assigned to use the device each day for 3 months (Experimental) and were compared with 33 subjects without the device (treatment-as-usual Control). All patients were instructed to complete baseline questionnaires and were assessed on thresholds of pressure pain and mechanical temporal summation as part of a standardized quantitative sensory test (QST) assessment. The subjects also uploaded smartphone applications (apps) for tracking use of the hfTENS and for daily pain assessment. Each participant completed weekly phone interviews, was prompted to complete daily pain app assessments, and was asked to repeat the baseline questionnaires again after 6 weeks and 3 months. Sixty percent of the subjects were female, 77.9% were Caucasian, and the average age was 46.2. Significant reductions in pain intensity (p<0.01) and activity interference (p<0.025) and significant improvements in pain catastrophizing (p<0.025) were noted in the Experimental subjects compared with the Controls. No group differences were found on depression, anxiety, or pain-related disability. Older subjects with a longer duration of pain tended to use the hfTENS more often. Subjects who showed greater sensitivity based on QST results revealed increased use of the hfTENS (p<0.025) and tended to believe that the hfTENS was more helpful in reducing their back pain, but these findings did not reach significance (p=0.09). Further trials designed to determine the mechanism of action of the hfTENS are needed. This article is protected by copyright. All rights reserved.