Aims: Primary aim of this study was to evaluate the inßuence of simultaneous local anesthesia on the clinical outcome after repetitive low-energy extracorpreal shock wave therapy (ESWT) for chronic tennis elbow. Methods: 51 patients were treated in a randomized single-blind international multicenter trial with a parallel-group design and blinded independent observer to evaluate low-energy ESWT with local anesthesia versus placebo ESWT with local anesthesia for patients with a chronic tennis elbow at three-month follow-up. 85% of patients of the verum group did not achieve good/ excellent results in the Roles & Maudsley score, they were offered once again application of the identical active treatment concept, this time without local anesthesia. 80% of the patients of the placebo group did not achieve good/excellent results, they were offered crossover therapy, i.e. identical active treatment with local anesthesia. Results: Reception of active therapy without local anesthesia resulted in excellent or good outcomes in 80% of patients of the original verum group at three-month follow-up, while application of active therapy with local anesthesia lead to good outcomes in 27% of the original placebo group (p= 0.0092, power= 0.8). Conclusions: Local anesthesia has a negative inßuence on the clinical outcome after repetitive low-energy ESWT for chronic tennis elbow.