RECENTLY, we have conducted a clinical study1 on several hundred patients who had undergone surgical treatment for carpal tunnel syndrome (CTS). Our aim was to establish whether on long-term follow-up the highly satisfying, immediate results of surgery persisted, and to determine what factors were useful in predicting postoperative outcome. The present report describes the results of the preoperative electromyographic examinations and their relationship to the clinical symptomatology and the postoperative prognosis. Material and Method Included in this study were all consecutive cases seen at the Mayo Clinic between 1956 and 1963 in which there was (1) a final diagnosis of carpal tunnel syndrome, (2) an electromyographic examination, and (3) surgical decompression of the median nerve., The number of patients fulfilling these criteria totaled 430. Of these, 117 did not complete or did not return a follow-up questionnaire or were deceased. Thirteen additional patients were rejected because they had