Abstract: Diagnosis of carpal tunnel syndrome is based on clinical findings and electrodiagnostic findings are used to confirm the diagnosis. On the other hand, sonography has enjoyed attention as a noninvasive method for diagnosis of carpal tunnel syndrome. 76 hands of patients in whom the diagnosis of carpal tunnel syndrome was confirmed and 80 hands in the control group were enrolled in the study. In both groups the surface area of median nerve was measured by sonography and electrodiagnostic studies were performed on the patient group. The patient group was followed up for at least 6 months. The difference between the surface areas of the median nerve measured by sonography was statistically significant (p < 0.0001). In the same way the difference between before and after operation Dash Score in the patient group was statistically significant (p< 0.001). Sonography was 95 % sensitive and 93 % specific for the diagnosis of carpal tunnel syndrome. A weak correlation was present between the severity of the disease in electrodiagnostic studies and sonography (p=0.047 and r=0380). No correlation was proved between the sonographic or electrodiagnostic findings and Dash score before or after the operation (p>0.05 and r<0.5). Based upon the findings of the present study, sonography may be a very suitable module for the diagnosis of carpal tunnel syndrome, but its finding or electrodiagnostic ones ' are not related to functional score of the patient. Answering the question whether it is a substitute for electrodiagnostic test needs further investigation. Key words: Carpal tunnel syndrome Ultrasonography Electrodiagnosis