objective: This study was conducted to assess effects of intramuscular stimulation (IMS) in comparison with that of dry needling and intramuscular electrical stimulation (IMES) in the patients with myofascial pain syndrome (MPS) of upper trapezius. METHOD: Thirty patients with MPS were assigned randomly to three groups, such as dry needling group (n=10), IMES group (n=10), and IMS group (n=10). In dry needling group, dry needling was applied to the trigger point of upper trapezius muscle. In IMES group, IMES was applied to the trigger point of upper trapezius muscle. In IMS group, IMS was applied to the trigger point of upper trapezius and parcervical muscles. Treatment were done three times a week for 2 weeks. Effects were assessed on 3rd day, 7th day and 14th day after treatment by visual analogue scale (VAS), McGill pain questionnaire (MPQ), and passive range of motion (PROM) of cervical spine. RESULTS: Significant changes of VAS and PROM were noticed in IMS group, compared with other groups. No significant difference of MPQ was noticed in IMS group, compared with other groups. CONCLUSION: IMS may be more effective treatment modality than dry needling and IMES in patients with MPS of upper trapezius muscle.