Management of acutely burned patients requires intense but meticulous fluid therapy. Indicators of satisfactory resuscitation include: intravascular and arterial pressures and urine output. The usefulness of these parameters as a predictor of cardiac index (CI) has not been tested. Compared to central venous pressure, right ventricular end-diastolic volume (RVEDV) may give a closer approximation of the preload of the right ventricle. Modifying the pulmonary artery (PA) catheter and using the thermodilution technique we measured RVEDV and right ventricular ejection fraction (RVEF) as well as the classical parameters in 16 patients of mean age 39.3 years and of mean body surface area burn 75.2%. CI best correlated with RVEDV (r = 0.75). Mean PA pressure, wedge pressure, RV end-diastolic pressure, and urine output correlated poorly with CI (r = 0.36, 0.32, 0.27, and 0.26, respectively). Unlike atrial pressures the RVEDV and RVEF are unaffected by malpositioning of transducers, airway pressure, and compliance changes of the ventricle. The measurement of RVEDV is a useful clinical tool for the assessment of preload and when used in combination with RVEF may indicate the need for inotropy.