• The serum uric acid levels and uric acid clearance rates were evaluated in 28 patients who had congenital heart disease. Based on hemodynamic assessments, the patients were divided into three groups: group 1, with normal cardiac output and normal arterial oxygen saturation; group 2, with hypoxemia (normal cardiac output with a decreased arterial oxygen saturation); and group 3, with cardiomyopathy (decreased cardiac output). The blood levels of uric acid were elevated in group 3. The mean serum uric acid levels were as follows: group 1, 4.2 mg/dL; group 2, 4.8 mg/dL; and group 3,11.7 mg/dL. All the patients in groups 2 and 3 had decreased uric acid clearance rates. The mean uric acid clearance rates were as follows: group 1, 10.1 mL/min/sq m; group 2, 4.2 mL/min/sq m; and group 3, 1.7 mL/min/sq m. The patients in group 3 had the most severe abnormalities. Patients with congenital heart disease may have marked impairment of their uric acid excretion, which can occur in the absence of significant renal disease, and may be found in acyanotic as well as cyanotic patients.