OBJECTIVE To assess the amount of additional information provided by measurements derived from pulmonary artery catheter (PAC) use beyond that derived from clinical evaluation by intensive care residents. METHODS One hundred forty-nine consecutive patients undergoing right-heart catheterization were prospectively included in the study. Before inserting a PAC, physicians had to predict pulmonary arterial pressure (PAP), pulmonary capillary wedge pressure (PCWP), systemic vascular resistance index (SVRI), cardiac index (CI), mixed venous oxygen saturation (SvO2), oxygen delivery (DO2), oxygen consumption (VO2), and pulmonary shunt fraction (Qs/Qt) by selecting a given option on a questionnaire. Ranges of options were chosen to create clear clinical differences among them. RESULTS The correct value was predicted in a median of 50% of cases (range, 45-63%). PAP was predicted correctly in 55%, PCWP in 46%, SVRI in 63%, CI in 62%, SvO2 in 45%, DO2 in 45%, VO2 in 51%, and Qs/Qt in 51%. A significant difference was found between estimated and measured values for all parameters (p < 0.01). No significant differences were detected between more and less experienced physicians. There was no significant difference between estimated and measured values with respect to the different courses of intensive care unit admissions or the different indications for PAC insertion. CONCLUSIONS In a selected group of critically ill patients, the PAC adds valuable and clinically relevant information to clinical assessment in about 50% of cases. Its use should not be withheld in patients with unclear hemodynamic and metabolic profiles.