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One of the methods for CTS diagnosis is to compare distal motor latencies between median and ulnar nerves. In the previous research distal motor latency (DML) of ulnar nerve was recorded from hypothenar area and the median nerve DML was recorded from thenar. In this research we recorded DML of ulnar nerve from thenar area and compared it with DML of median nerve. The aims of this research is to shorten the process of electro diagnosis by preserving the sensitivity. The type of the research is diagnostic clinical trial on 42 normal person and 64 patients with CTS that referred to department of physical medicine and rehabilitation of Shohada Tajrish Hospital in fall and winter of 2000-01 participated in this research. The result of the research is analyzed by student T-test method. The DML of ulnar nerve recorded from thenar in normal persons was 3.52±0.5 ms and the difference between median and ulnar nerve recorded from thenar was 1.23 ms. The P-value of the study were less than 0.0001 that is significant thus this method can be used for diagnosis of CTS.