BACKGROUND: The purpose of this study was to measure and compare the optimum depth of the internal jugular venous catheterization between the right and left side. METHODS: Forty-four patients were enrolled for this study and divided into two groups (22 patients each). The optimum depth of the catheterization was calculated using the sum of two component (A and B); the advanced length of the catheter from the level of the cricoid cartilage (A) and the distance from the catheter tip to the junction of the superier vena cava and right atrium (B). RESULT: The optimum depths of the internal jugular venous catheterization were 16.0 1.0 cm (right) and 18.4 1.5 cm (left) respectively. Left side was significantly longer than right side (p<0.05). In this study, we experienced some complications; arterial punctures (5 cases) and migration of the catheter to the opposite subclavian vein (1 case). Five complications were associated with left internal jugular venous cannulation and one was associated with the right side cannulation. CONCLUSION: We concluded that the optimum depth of the internal jugular venous catheterization was longer in the left side than in the right side.