OBJECTIVE: To investigate the effect and optimal therapeutic frequency of extracorporeal shock wave therapy (ESWT) on upper limb spasticity in chronic stroke patients. METHOD: Total 16 patients with chronic stroke were evaluated. Patients were divided into 2 groups, one group applied with 4 Hz stimulation, and the other group applied with 8 Hz stimulation. All patients were applied with sham stimulation (0 mj/cm2) at the initial time and with active stimulation (0.030 mj/cm2) 4 weeks later. Target muscles were dorsal interossei and flexor digitorum profundus. The primary outcome was the finger flexor spasticity using the modified Ashworth scale (MAS), which was serially measured before, after 1 week and after 4 week respectively. RESULTS: Before the study, the MAS of 4 Hz group was 3.90±0.87 and 8 Hz group was 3.89±0.93, which showed no significant difference. After 1 week of active stimulation, the MAS of 4 Hz group (2.90±0.81) was significantly smaller than the MAS of 8 Hz group (3.33±0.88). Treatment effects had been continued to 4 weeks. There were no complications associated with ESWT. CONCLUSION: ESWT could be used to reduce spasticity of the upper limb muscles in chronic stroke patients.