The efficacy of transcutaneus electrical nerve stimulation in the treatment of myofascial pain syndrome - In this study, the effectivity of Transcutaneous Electrical Nerve Stimulation (TENS) was investigated in the treatment of Myofascial Pain Syndrome (MPS) due to the presence of trigger points in the upper portion of trapezius muscle. For this purpose, our study included 3 groups with 16 patients each (total of 48 patients). TENS was administered 100 Hz, 100 usn just a little above the sensation threshold in the first group, 2 Hz, 100 usn a little above the sensation threshold in the second group and placebo in the third group.Each patients was examined four times during the study; before the initiation of the treatment just after the first treatment, at the end of the first week and at the end of the second week. Pain, sensitivity and cervical lateral flexion values were used as evaluation parameters. As a result; both types of TENS were found to be beneficial in the treatment of MPS and it was shown that beneficial effects of high frequency TENS was observed earlier. Placebo TENS was equally effective as the other types of TENS for the pain reduction and the increase of range of motion at the end of second week. Reduction in the sensitivity was seen earlier in the group which was administered high frequency TENS and more prominent than the other groups with TENS. Reduction inthe sensitivity was also seen earlier in the group which was administered low frequency TENS than the control group but there was no statistical significance at the end of second week. In conclusion; TENS was found to be effective in the treatüment of MPS and high frequency TENS as more effective than low frequency TENS and plaebo TENS.