A patient is presented in whom pulmonary artery catheter insertion fortutiously demonstrated persistent left superior vena cava on two separate occasions. Further studies with venogram and a first pass nuclear scan demonstrated total absence of the right superior vena cava. Although this anomaly is commonly associated with intracardiac defects and rhythm disturbances only the latter was seen in our patient. Invasive hemodynamic monitoring is frequently performed in the majority of modern intensive care units. The bedside technique used for insertion of a Swan-Ganz catheter using only pressure monitoring for advancing the catheter has relatively few complications. One such complication is misplacement along an anomalous route where the catheter may take to the heart. We have recently treated a patient on two separate occasions who had a persistent left superior vena cava with absent right superior vena cava.