In 1973, mass screening program for 6-month old infants for early detection of neuroblastoma using a VMA spot test of a urine sample was initiated in Kyoto. In 1985, nation wide mass screening was initiated throughout the entire country and the Government has given the financial support to each district. In 1988, the Government recommended the institution of mass screening by quantitative measurements of VMA, HVA and creatinine using HPLC (high performance liquid chromatography), instead of the qualitative test of VMA alone. From 1974, at the time of initiation of mass screening for neuroblastoma to the end of October, 1989, 383 cases with this tumor have been discovered throughout the screening program. Three hundreds eighty three cases (88%) of them had been registered to the Neuroblastoma Committee of the Japanese Society of Pediatric Oncology. In this paper, the mass screening program was introduced and the 337 cases with this tumor detected by 6-month old screening were analyzed their clinical symptoms, findings, urinary VMA and HVA levels, primary sites, weights of primary tumor, histology, stages at diagnosis, metastatic sites, and the results of the treatment. Three hundreds twenty eight cases (97%) of them are expected to be cured. And we discussed clinical problems related to mass screening program for neuroblastoma, such as an increase of the incidence of infantile neuroblastomas detected by this program and the spontaneous regression.