We have investigated the effect of dichloroacetate (DCA) on the urinary excretion of lactate and pyruvate in a patient with congenital lactic acidosis and in healthy human controls. DCA administered orally in doses of 50 mg/kg and 30 mg/kg decreased plasma lactate and pyruvate of both the patient and the controls, while the urinary excretion of lactate and pyruvate was increased. However, these urinary increments were too small to contribute to the decrease of plasma lactate and pyruvate.