To avoid fatal complications of central venous catheterization such as cardiac tamponade, the tip of the central venous catheter (CVC) should be placed outside of the cardiac chamber. To suggest a guideline for a proper depth of CVC in infants, we measured the distance from the skin puncture site to the junction between superior vena cava and right atrium (SVC-RA junction) by using transesophageal echocardiography (TEE). Fifty infants less than 5 kg undergoing surgery for congenital heart disease were enrolled in this prospective study. After the induction of general anesthesia, CVC was inserted via the right subclavian vein. After the tip of the CVC was placed at the SVC-RA junction using TEE guidance, the length of the CVC inserted beneath the skin was measured. The measured distance had a high correlation with the patient's height, weight, and age (r = 0.88, 0.76, and 0.64, respectively). In infants smaller than 5 kg, the following guideline can avoid intraatrial placement of the CVC: a depth between 40 and 45 mm for infants 2.0-3.0 kg in weight, 45-50 mm for those 3.0-3.9 kg, and 50-55 mm for those more than 4.0 kg.