By March 1992, 166,959 infants were screened in Sapporo City, and 35 patients were found to have this tumor. Incidence of this tumor in our screening was one among 5,059 babies examined. 2) Eleven infants among the group with negative screening at 6 months developed neuroblastoma later. The patients developed tumors one to several years after mass screening, and 2/3 of these cases showed high urinary HVA compared to VMA. 3) We postulate that some of the adrenal steroids, possibly cortisol, may play a role for the malignant progression of this tumor.