OBJECTIVE: To evaluate the correlation of electrodiagnostic severity, severity of symptom, and clinical severity in carpal tunnel syndrome (CTS). METHOD: The sixty eight patients with documented CTS in outpatient clinic from January, 2000 to June, 2001 were included (9 male, 59 female, averaged age 50.0+/-8.8 years). We evaluated the severity of symptom, functional status of ADL with the Levine' questionnaire, and clinical severity with 3 kinds of examination (thenar atrophy, sensory change, and Phalen's test). The electrodiagnostic severity was classified according to Stevens' classification and compared with the severity of symptom, functional status, and clinical severity. RESULTS: The electrodiagnostic severity was classified into three degrees. Five patients (7.4%) were classified into mild degree, 32 patients (47.1%) moderate degree, 31 patients (45.6%) severe degree. The average of severity of symptom scores were 28.4+/-8.5, 31.8+/-7.4, and 31.8+/-9.1 respectively, and there was no significant difference (p>0.05) between the groups. Functional status scales were 14.2+/-6.7, 15.6+/-5.4 and 18.9+/-7.0 respectively and no significant difference (p=0.07) but there was a tendency that the severer was electrodiagnostic severity, the more decreased functional status scale. The clinical severity showed a significant correlation with the electrodiagnostic severity (p<0.05). CONCLUSION: The electrodiagnostic severity has a significant correlation with the clinical severity, but not with the severity of symptom, the functional status in CTS.