The causes of unsatisfactory results after surgery for carpal tunnel syndrome were retrospectively analysed in forty cases. The most common pathological finding was fibrosis and adhesions in the carpal canal. Technical errors were found in 43%. In 30% other neuropathies were present and bilateral operations had been performed in 55%. It is possible that there is a tendency to develop CTS in these patients. The results after epineural dissection or internal neurolysis were comparable to those after external neurolysis.