Pulmonary arterial hypertension is a malignant disease with a median survival of 3 years. Uric acid levels are elevated in severe heart failure and in states of hypoxemia. Early data suggest a correlation between hyperuricemia and severe pulmonary arterial hypertension. We studied 29 patients with pulmonary arterial hypertension diagnosed and treated between 1998 and 2001. Clinical characteristics (6 min walk test and New York Heart Association class) and hemodynamic parameters (pulmonary artery pressure, pulmonary vascular resistance and cardiac output) were evaluated and correlated to uric acid level in a retrospective study. Uric acid levels correlated positively with New York Heart Association class (r=0.66, P<0.001) and negatively with 6 min walk test (r=-0.35, P=0.03). Uric acid levels were higher in patients who died than in patients who survived at the end ofthe follow-up period (8.8 vs. 5.7 mg/dl, P=0.001). This study shows that uric acid levels are elevated in severe pulmonary arterial hypertension and can be used as a prognostic marker of disease severity.