Use of the balloon-tipped (Swan-Ganz) pulmonary artery catheter has increased in recent years. The device has three fundamental applications: pressure measurement, flow measurement, and blood sampling. Like any invasive procedure, this catheter should be used only after careful assessment of factors that affect its risk/benefit ratio. There must be a well-defined indication for the procedure. Physicians must be aware of the factors that can influence the validity of the measurements. Familiarity with the technical details of the procedure and with potential complications and how to avoid or manage them is essential to minimize risks and increase the likelihood of obtaining useful information.