BACKGROUND: The optimal depth of subclavian catheterization is not clearly and simply defined in the pediatric population. The aim of this study is to examine the relationship between the depth of the subclavian catheter and easily measured body-size variables, such as weight and height, and then to formulate a guide for the optimal depth of subclavian catheterization in the pediatric population. METHODS: We cannulated eighty-five pediatric cardiac patients via the left or right subclavian approach. The position of the catheter tip was determined by postoperative AP chest x-ray, and the length from the skin to the point of the border of superior vena cava and the right atrium (SK-SVCRA) was measured. RESULTS: Significant correlations with SK-SVCRA were found for weight and height. For the right approach, SK-SVCRA is calculated as 0.28xweight (kg) + 4.86 or 0.07 x height (cm)+1.70. For the left approach, SK-SVCRA is calculated as 0.22xweight (kg)+6.51 or 0.06xheight (cm)+3.94. CONCLUSIONS: Simple equations for the placement of the catheter tip at the border of the superior vena cava and right atrium as a function of patients' weight and height were formulated. These data may provide a useful guide to determine how deeply the subclavian catheter should be located.