Between 1991 and 1996 three cases of MCAD-deficiency (medium-chain-acyl-Co-A dehydrogenase deficiency) were diagnosed in the Vestische Kinderklinik. All patients showed hypoketotic hypoglycaemia with hyperuricaemia. In the group of hypoketotic hypoglycaemia without lactat acidosis MCAD-deficiency is the only metabolic disease presenting regularly with hyperuricaemia. Thus, hyperuricaemia in a patient with hypoketotic hypoglycaemia is a strong indicator for MCAD-deficiency. Measurement of uric acid is easily available before sophisticated metabolic analysis are completed.