OBJECTIVE: To acknowledge whether flexion or extension of wrist joint produces any changes in median nerve conduction of the diabetes with or without polyneuropathy. METHOD: With thirty healthy adults selected as control, 33 diabetes with polyneuropathy (Group I) and 21 diabetes without polyneuropathy (Group II) were studied. Before the study, the wrist joint was positioned in flexion or extension for 5 minutes. The variables used for the statistic analysis were mean changes of latencies and amplitudes in the median motor and sensory responses in neutral, flexed, and extended position. RESULTS: After wrist flexion or extension, there was no significant difference in the mean change of latencies and trans-carpal conduction velocities between Group I and Group II in the median motor and sensory nerve conduction studies, and in the mean change of amplitudes between the two groups in the median motor nerve study. But, there was significant difference in the mean change of amplitude between Group I and Group II in the median sensory nerve study after wrist extension. CONCLUSION: We conclude that the change of amplitude in median nerve conduction study in different wrist position may be helpful to detect carpal tunnel syndrome with diabetic polyneuropathy in its early stage.