BACKGROUND: Extracorporeal shock wave therapy (ESWT) is one of the treatment options used for patients with myofascial pain syndrome (MPS), although its effectiveness is controversial. The purpose of this study was to evaluate the effectiveness of ESWT in the treatment of MPS in terms of pain relief and functional improvements. METHODS: We assessed 93 patients with MPS who underwent ESWT from March 2009 to July 2014. After exclusion of 25 patients with shoulder diseases, 68 patients were enrolled in the study. The mean follow-up period was 7.5 months (± 4.2 weeks), and the average duration of symptoms was 5 months (range, 2-16 months). ESWT was applied to intramuscular taut bands and referred pain areas once a week for 3 weeks. Visual analog scale (VAS) pain scores and American Shoulder and Elbow Surgeons (ASES) scores were obtained at an initial assessment and at the 6-week, 3-month, and 6-month follow-up assessments. RESULTS: VAS pain scores and ASES scores improved significantly after 3 sessions of ESWT (p<0.05). Both scores were improved, although not significantly, after 6 weeks (p>0.05). CONCLUSIONS: ESWT is an effective treatment option for patients with MPS.