Neuroblastoma is the commonest solid tumour in children under the age of 5 years (50% of cases before 2 years, 90% before 5) and the second cause of death after accidents. Approximately one child in 10,000 develops neuroblastoma by the age of 15 years. The situation in other European and North American countries is similar to that in France. As neuroblastoma is derived from the sympathetic nervous tissues, it is associated with the production of large amounts of catecholamines and their metabolites which are excreted in the urine. Less than 5% of cases do not produce catecholamines. Vanillylmandelic acid (VMA), homovanillic acid (HVA) and dopamine (DA) are the most useful chemical markers for the diagnosis and clinical control of neuroblastoma. They are generally measured using the reliable and sensitive high pressure liquid chromatography (HPLC). Survival is related to stage (the Evan's staging protocol has been superseded by the INNS staging), and age at diagnosis. There is almost 100% survival for stages I and IIa before the age of 12 months, and less than 20% for stage IV when diagnosed after 2 years of age. Multiple copies of the N-myc oncogene, deletions of chromosome 1p, and diploidy in tumour cells are associated with poor prognosis.(ABSTRACT TRUNCATED AT 250 WORDS)