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Background: A recent report has suggested that local injection of botulinum toxin type A is an effective method of treatment for chronic tennis elbow. The toxin is thought to provide temporary paralysis of the painful common extensor origin, thereby allowing a healing response to occur. To test this theory, we performed a double-blind, randomized, controlled, pilot trial comparing injections of botulinum toxin type A with those of a placebo (normal saline solution) in the treatment of chronic tennis elbow. Methods: Forty patients with a history of chronic tennis elbow for which all conservative treatment measures, including steroid injection, had failed were randomized into two groups. Half the patients received 50 units of botulinum toxin type A, and the remainder received normal saline solution. The intramuscular injections were performed 5 cm distal to the maximum point of tenderness at the lateral epicondyle, in line with the middle of the wrist. The two solutions used for the injections were identical in appearance and temperature. The results of a quality-of-life assessment with the Short Form-12 (SF-12), the pain score on a visual analogue scale, and the grip strength measured with a validated Jamar dynamometer were recorded before and three months after the injection. Results: Three months following the injections, there was no significant difference between the two groups with regard to grip strength, pain, or quality of life. Conclusions: With the numbers studied, we failed to find a significant difference between the two groups; thus, we have no evidence of a benefit from botulinum toxin injection in the treatment of chronic tennis elbow. Level of Evidence: Therapeutic Level II. See Instructions to Authors for a complete description of levels of evidence.