Background: The aim of this study is to identify the correlation between ultrasonographic findings of median nerve and clinical scale and electrophysiologic data in carpal tunnel syndrome. Methods: Forty three patients (79 hands) with electrophysiologically confirmed carpal tunnel syndrome were evaluated. Clinical symptoms were examined by Historical-Objective (Hi-Ob) scale. Electrophysiologic data and Padua scale were used for severity of electrophysiology. In ultrasonographic study, cross sectional area and flattening ratio of median nerve were measured at distal wrist crease level (DWC), 1cm proximal to distal wrist crease level, and 1cm distal to distal wrist crease level. The correlation between Hi-Ob scale, electrophysiologic data and ultrasonography was measured with Spearman rank test. Results: The mean Hi-Ob scale was 2.4. Mean Padua scale was 4.0. In ultrasnonographic study, cross sectional area and flattening ratio were $0.112;cm^2{pm}0.025$ and $3.0{pm}0.6$ at 1cm proximal to DWC level, $0.118{pm}0.026;cm^2$ and $2.9{pm}0.4$ at DWC level, and $0.107{pm}0.032;cm^2$ and $3.0{pm}0.4$ at 1 cm distal to DWC level. Hi-Ob scale was not correlated with cross sectional area and flattening ratio of median nerve. Hi-Ob scale was correlated with Padua scale positively (r=0.44) and correlated with amplitudes of CMAP and SNAP, negatively (r=-0.33; r=-0.30). Cross sectional area of median nerve was significantly correlated with Padua scale, amplitudes and latencies of CMAP and amplitudes of SNAP. Conclusions: Ultrasonographic findings of median nerve and electrodiagnostic data had statistically significant correlation. Consequently, ultrasonography could be an adjunctive method in diagnosis of carpal tunnel syndrome.