This study was undertaken to better define the relationship between catecholamine (CAT) metabolism within the malignant neuroblast and other factors known to influence clinical outcome in neuroblastoma (NB). Several CATs and their metabolites were measured in 32 tumors and 47 urines from 60 newly diagnosed children with neurogenic tumors. Absolute and relative CAT concentrations were correlated with age, clinical stage, histologic differentiation and survival duration. The major findings are: (1) urinary CAT excretion patterns often differ markedly from tumor CAT patterns in the same child, which may be explained by the continuous nature of tumor metabolism, hepatic and renal catabolism, and sampling errors; (2) definite patterns of biochemical maturation are apparent in tumors and urines, but standard light microscopy is insufficient to correlate this with degree of histologic differentiation; (3) more differentiated patterns of CAT metabolism, both in tumor and urine, are significantly associated with age less than 1 year at diagnosis, and with more favorable clinical Stage (I, II, IVS). Tumor NE was increased relative to DM and DA, and urine NMN and VMA were increased relative to DM and HVA, in these patients. (4) this more differentiated CAT pattern in infants and in less advanced stages was reflected in their better survival. Greater maturity of tumor enzyme systems is the probable reason for the better prognosis of NB in infants less than 1 year. Individual enzymes should be measured in fresh tumor tissues, and related to relative and absolute CAT concentrations in tumor and urine, to try to categorize patients on the basis of clearcut biological differences when planning new treatment strategies for NB.