Previous reports have shown hemodynamic data inaccurately predicted by physical examination and x-ray findings. Although invasive hemodynamic monitoring has been shown to significantly alter the management of critically ill patients, the impact on mortality has been difficult to assess. In a prospective study of 35 patients, we found inaccurate predictions of left and right heart filling pressures by clinical assessment. However, cardiac output was accurately estimated. Management was altered 34% of the time because of invasive hemodynamic assessment; however, mortality was not affected by a change in therapy.