In this article, several technical and physiologic factors that might interfere with the accurate interpretation of the pulmonary artery wedge pressure as an indicator of LV preload and extravascular lung water have been reviewed. The purpose of this article is not to belittle the use of the wedge pressure value but, instead, to stress the importance of precise measurement and careful interpretation of this parameter. Every effort must be made by the critical care nurse at the bedside to minimize erroneous data and to optimize the validity of the wedge pressure value in order to prompt appropriate clinical decisions.