Objective To investigate the electrophysiological characteristics of carpal tunnel syndrome (CTS) and CTS-associated cervical spondylotic radiculopathy (CSR),and to examine the relationship between CTS and CSR. Methods The clinical characteristics and electrodiagnostic features of 81 patients with CTS and 20 patients with both CTS and CSR (the double crush,DC) were analyzed and compared.The data were analyzed according to the severity of the deficit in median nerve conduction using electromyography. Results The 81 patients with CTS had 123 median nerves with abnormal conduction (39 cases with unilateral abnormalities and 42 cases with bilateral abnormalities).The 20 patients with DC had 31 median nerves with abnormal conduction (9 cases with unilateral abnormalities and 11 cases with bilateral abnormalities).The rate of abnormal sensory nerve conduction velocity (SCV) was 100％ in C6 and C7 level radiculopathies.The rate of abnormal distal motor latency (DML) was 92.31％ in C5 level radiculopathies.There was a statistically significant difference between CTS and DC in the rate of abnormal SCV from the middle finger to the wrist.The other electrodiagnostic data were not significantly different between the CTS and DC patients.Neurophysiological tests were used to grade CTS into categories according to the American Association of Electrodiagnostic Medicine's criteria,but there was no statistically significant difference between CTS and DC. Conclusions CSR lesions on a proximal nerve root may cause the nerve to be more susceptible to distal injury and increase the risk of CTS.The findings support the DC hypothesis,but DC on a median nerve did not result in more severe injury than a single crush.