Tyrosine and tryptophan, as well as 26 metabolites of these amino acids, were analyzed simultaneously in urine specimens from patients with neuroblastoma and control infants by a three-dimensional HPLC system to develop an early diagnosis. 2. Levels of detected compounds in urine from patients with neuroblastoma were generally higher in the case of catecholamines and lower in the case of indolalkylamines than those in controls. 3. The pathways of Dopamine-3,4-Dihydroxyphenylacetic acid-Vanillylmandelic acid, Dopamine-3-Methoxy-4-hydroxyphenylethylene glycol-Vanillylmandelic acid and Tyrosine-4-Hydroxyphenylacetic acid-4 were, in particular, found to be active in patients with neuroblastoma.