Malignant disease was diagnosed in 404 of 38,967 children admitted to a hospital during six and one-half years. In children less than one year old, renal and adrenosympathetic tumors were the most frequent type. Thereafter leukemia and lymphoma predominated until the age of 8 years. In the 10-to-13-year age groups, inclusive, tumors of the central nervous system and eye predominated. Twelve cases of bone tumor were observed, all in children past their second birthday. About one-third of the 404 patients came to medical attention because of a mass. The most frequent error at the initial examination was a diagnosis of upper respiratory infection. The two types of malignancy most frequently misdiagnosed were Hodgkin's disease and neuroblastoma. The fact that 75% of those who died from malignant disease were dead at the end of the first 12 months indicates the need for prompt action when the diagnosis is made.