The prevalence of pulmonary hypertension in 507 patients hospitalized with portal hypertension but without known pulmonary hypertension who underwent cardiac catheterization was prospectively studied. Ten (2%) of these patients, 6 of whom were clinically asymptomatic, had primary pulmonary hypertension. Second, 26 patients with symptomatic pulmonary hypertension complicating portal hypertension were reviewed. Pulmonary hypertension occurred later after diagnosis of portal hypertension in patients with a surgical shunt (10 patients) than in those without a shunt (147 +/- 49 vs. 44 +/- 27 months; P less than 0.0001). Cardiac index correlated inversely with pulmonary arterial pressure (r = -0.45; P less than 0.01) and was lower in the 5 patients who died of pulmonary hypertension than in the 5 who died of liver failure (1.52 +/- 0.14 vs. 3.69 +/- 1.88 L/min.m2; P less than 0.05). Third, systemic and splanchnic hemodynamics were compared in 285 patients with alcoholic cirrhosis and 29 controls. No significant relation was found between elevated pulmonary vascular resistance and increased portal pressure, zzygos blood flow, or cardiac index. Pulmonary hypertension is considerably more frequent than was previously estimated in patients with portal hypertension. The risk of developing pulmonary hypertension could increase with the duration of portal hypertension without any clear relation to the degree of portal hypertension, hepatic failure, or amount of blood shunted.