The left pericardiacophrenic vein was accidentally cannulated during an attempt to establish central venous catheterization through the left internal jugular vein. Chest roentgenograms and intravenous contrast material confirmed the position of the catheter. Although our patient developed no problems during a five-day cannulation, based on published information, it is advisable to reposition the catheter to avoid perforation of the pericardiacophrenic vein and possible cardiac tamponade.