Swan-Ganz catheter (SGC : pulmonary artery catheter) was introduced in clinical use by Swan HJ and Ganz W in 1970. Since then, the catheter has been used in many kinds of clinical fields, such as critical care medicine, cardiovascular surgery, anesthesia, and cardiology, because of its useful functions. SGC can easily advance into the pulmonary artery with its flow-directed balloon. The central venous pressure (CVP), the pulmonary artery pressure (PAP), and the pulmonary capillary wedge pressure (PCWP) can be measured, and cardiac output is obtained by thermodilution method. These days, SGC also has continuous cardiac output measurement system and mixed venous blood oxygen saturation monitoring system. Continuous cardiac output system automatically works by heating blood in the right atrium and ventricle with thermal filament periodically. Although SGC gives full diagnostic and therapeutic information of critically ill patients or cardiac surgical patients, all of the patients can not survive their tough critical clinical situation struggling with complications. Therefore, SGC has to be applied to the patients after thorough consideration whether the patients receive benefit of the catheter or not. Furthermore, the data obtained from SGC must be carefully interpreted to manage the patients.