Background: On the basis of observational trials, numerous investigators have recommended extracorporeal shock wave therapy as an alternative treatment for chronic lateral epicondylitis of the elbow. However, there has been no evidence of its efficacy from well-designed randomized clinical trials. The objective of this study was to find out whether extracorporeal shock wave therapy in combination with local anesthesia was superior to placebo therapy in combination with local anesthesia. Methods: A randomized multicenter trial with a parallel-group design was conducted. Following administration of local anesthesia, either extracorporeal shock wave therapy with three treatments of 2000 pulses each and a positive energy flux density (ED+) of 0.07 to 0.09 m J/mm2 or placebo therapy was applied on an outpatient basis. Treatment allocation was blinded for patients and for observers. The primary end point was based on the rate of success, as determined with the Roles and Maudsley score and whether additional treatment was required, twelve weeks after the intervention. Crossover was possible after assessment of the primary end point. Secondary end points were the Roles and Maudsley score, subjective pain rating, and grip strength after six and twelve weeks and after twelve months. The planned number of 272 patients was included in the study. Results: The primary end point could be assessed for 90.8% of the patients. The success rate was 25.8% in the group treated with extracorporeal shock wave therapy and 25.4% in the placebo group, a difference of 0.4% with a 95% confidence interval of -10.5% to 11.3%. Similarly, there was no relevant difference between groups with regard to the secondary end points. Improvement was observed in two-thirds of the patients from both groups twelve months after the intervention. Few side effects were reported. Conclusions: Extracorporeal shock wave therapy as applied in the present study was ineffective in the treatment of lateral epicondylitis. The previously reported success of this therapy appears to be attributable to inappropriate study designs. Different application protocols might improve clinical outcome. We recommend that extracorporeal shock wave therapy be applied only in high-quality clinical trials until it is proved to be effective.