Since April 1981, the city of Sapporo, Japan, has conducted a mass screening program to measure urinary vanillylmandelic acid and homovanillylic acid using high-performance liquid chromatography. This program was expanded to the entire island of Hokkaido in October 1987. Mass screening proved beneficial, resulting in an increase in patients diagnosed with neuroblastoma under 1 year of age from 17% to 66%, an increase in stage I cases from 9% to 26%, an increase in stage III cases from 9% to 32%, and an increase in the tumor resectability rate from 15.1% to 58%. These improvements raised the 5-year survival rate for neuroblastoma from 23% to 66.7%. An additional study of these mass screening cases using Shimada's classification showed a wide range of histopathological distribution, and it demonstrated the usefulness of such a program in identifying the tumors most in need of early treatment.