Menkes disease is a disorder of copper transport that results in early death. Early therapy with parenteral copper-histidine has been shown to markedly improve outcomes. However, early diagnosis is difficult because patients are asymptomatic in early infancy. In Menkes disease, impaired activity of dopamine beta-hydroxylase, a copper-dependent enzyme, leads to increased urine ratios of homovanillic acid/vanillylmandelic acid (HVA/VMA). Urine HVA/VMA ratios ranged from 4.1 to 69.7 among 15 patients with Menkes disease, whereas only 0.18% of controls had ratios greater than 4.0. Thus, the urine HVA/VMA ratio is a useful screening method for Menkes disease.