Objective:To evaluate the effectiveness of radial extracorporeal shock wave therapy on ankle flexor spasticity in stroke survivors and to reveal changes in the fibroelastic components of muscle.Design:Randomized controlled trial.Setting:Inpatient neuro-rehabilitation clinic of a university hospital.Participants:Stroke patients with ankle flexor spasticity.Interventions:Patients were randomized to three groups; radial extracorporeal shock wave therapy, sham, or control. Active and sham therapy were administered two sessions/week for two weeks. All patients received conventional rehabilitation.Main measures:The primary outcome was Modified Ashworth Scale. Secondary outcomes were the Tardieu Scale and elastic properties of plantar flexor muscles assessed by elastography (strain index). All assessments were performed before, immediately after the treatment, and four weeks later at follow-up.Results:Fifty-one participants were enrolled (active therapy n n＝17, sham n n＝17, control n n＝17). Modified Ashworth scores showed a significant decrease in the active therapy group (from 2.47±0.72 to 1.41±0.62) compared to sham (from 2.19±1.05 to 2.06±1.12) and control (from 2.06±0.85 to 2.00±0.73) groups immediately after the treatment (n P<0.001). Tardieu results were also in concordance (n P<0.001), however this effect was not preserved at follow-up. Elastic properties of the ankle flexors were improved in all groups at both assessments after the therapy showing significant decreases in strain index (n P<0.001). However, there was no difference among the groups in terms of improvement in elastography.n Conclusion:Radial extracorporeal shock wave therapy has short-term anti-spastic effects on ankle flexor muscles when used as an adjunct to conventional rehabilitation.