The clinical histories and post-mortem findings in five cases of neuroblastoma are described, and an account given of the microscopic characteristics of the tumours. In four of the cases the tumour was present at birth and was probably so in the fifth case. In only one case was the presence of the malignant tumour a significant factor in causing death. The differential diagnosis of such tumours is discussed.The accumulated evidence of many recorded cases suggests that neuroblastoma, becoming manifest in the early months or weeks of life, and congenital tumour, would be included in such a group, and has an appreciably better prognosis than has this same tumour when it becomes manifest in later childhood. The literature is briefly reviewed to illustrate this aspect of prognosis and possible reasons for it are indicated.