Pulmonary artery wedge pressure is used in the diagnosis and management of critically ill patients. This measurement provides an accurate assessment of hemodynamic status, cardiac function and venous oxygen saturation. Wedge pressure monitoring has been used in the management of patients with complicated myocardial infarction, refractory heart failure, circulatory shock, pulmonary edema and other critical illnesses. Because measuring the pulmonary artery wedge pressure is an invasive procedure, the value of the additional data provided by monitoring should be considered carefully before choosing this method. Clinical assessment or noninvasive tests, including chest radiographs and echocardiography, often provide information adequate for planning management. If therapy fails, or if noninvasive data are uncertain, pulmonary artery catheterization is appropriate. Risks and complications may be secondary to either catheter insertion or the continued presence of the catheter.