A paucity of data exists as to the relation of mean right atrial pressure (RAP) to Doppler parameters of right atrial and ventricular filling. Furthermore, whether echocardiographic parameters of right atrial and right ventricular function and inferior vena cava improve the relation of Doppler filling dynamics with RAP has not been explored. Doppler and echocardiographic studies were performed simultaneously with measurements of mean RAP in consecutive patients who either had a central venous catheter in the Intensive Care Unit or underwent catheterization of the right side of the heart. The initial population consisted of 35 patients with a mean age (+/-SD) of 60+/-15 years; 34% were on mechanical ventilation. Mean RAP averaged 9+/-5.7 mm Hg (range, 2 to 28 mm Hg). Among tricuspid inflow parameters, the strongest relation with RAP was observed with the ratio of early to late velocity (r=.66). For hepatic venous flow, systolic filling wave indexes had the best relation with atrial pressure, the highest being for systolic filling fraction (r=-.86). Weaker relations were noted with the use of right atrial volumes, right ventricular function, and inferior vena caval diameters. The addition of any of these variables did not improve the relation of systolic filling fraction with RAP. The regression equation (RAP=21.6-24 systolic filling fraction) was tested prospectively in the estimation of atrial pressure 50 patients. The correlation coefficient was .89 in the prospective group and .88 in the total group of 85 patients. The mean difference between predicted and actual pressures in the whole population was -0.2+/-2.6 mm Hg. The sensitivity and specificity for mean RAP>8 mm Hg were 86% and 92%, respectively. Among echocardiographic and Doppler parameters of right atrial and right ventricular function, hepatic venous flow dynamics relate best to mean atrial pressure and can be used clinically to estimate mean RAP.