Objective To assess the effectiveness of nocturnal splinting on carpal tunnel syndrome （CTS） by clinical scores and nerve conduction studies （NCS）, and explore their correlations.Methods Forty-one patients （64 wrists）, chosen from 66 consecutive patients with CTS from April 2009 to January 2010 meeting the inclusion criteria, were enrolled. The enrolled subjects were clinically evaluated by symptom severity scale （SSS） and functional status scale （FSS）, and electrophysiologically evaluated by conventional nerve conduction studies （NCS）; distal motor latency （DML） of wrist-abductor pollicis brevis, sensory conduction velocity （SCV） of wrist-index finger and wrist-ring finger, and the differences of distal sensory latency between the median and ulnar nerves （△DSL） were measured. The patients were instructed to use each splint on dorsal and palmar surface of the hand, centered at the distal wrist crease, to fix the wrist in neutral posture at bedtime. SSS, FSS and NCS were evaluated before splinting and （3.03±1.16） months after splinting; the follow-up was completed in 29 patients （31 wrists）.Results （1） The abnormality rates of DML, wrist-index finger SCV, wrist-ring finger SCV and△DSL were 85.9%, 78.1%, 81.3% and 96.9%, respectively. （2） The SSS scores （1.55±0.38）, FSS scores （1.40±0.27） and△DSL （1.24±0.61） after splinting was significantly decreased as compared with those before splinting （1.77±0.38, 1.53±0.31, 0.97±0.60）; and the DML [4.14±0.76 （ms）] after splinting was significantly shortened as compared with that before splinting [4.53±1.25 （ms）]. No improvement of clinical scores was noted in 9 patients （14 wrists, 45.8%） after splinting. （3） The SSS scores were less significantly correlated to DML （r=0.420, P=0.019）, wrist-index finger SCV （r=-0.425, P=0.017）,wrist-ring finger SCV （r=-0.519, P=0.003）, and no correlation between SSS scores and△DSL was noted （r=0.189, P=0.309）; no correlation between FSS scores and the parameters of NCS was found either （P〉0.05）. Conclusions Splinting is effective at least in a short-term in more than halfpatients with CTS.Little correlation is noted between clinical scores and NCS, suggesting that utilization both approaches to assess the therapeutic effect is of more significance. △DSL is the most sensitive parameter in the electrodiagnosis of CTS.