Through a nationwide questionnaire survey, data regarding diagnosis, treatment, and clinical course were obtained on 60 cases of Wilms' tumor in 1956, on 108 cases of Wilms' tumor in 1962, on 84 cases of neuroblastoma in 1956, and on 142 cases of neuroblastoma in 1962. Survival curves for patients with Wilms' tumor showed a significant improvement in 1962 compared with 1956. This change occurred in children of all ages without metastases at the time of first examination and in children 2 years of age and older with metastases at first examination. The improvement in survival curves among children with Wilms' tumor is attributed to the addition of actinomycin-D, vincristine, and cyclophosphamide to the treatment regimens in 1962. Although the intensity of chemotherapy increased from 1956 to 1962, the survival curves for children with neuroblastoma showed no statistically significant differences between the two time periods. With either tumor without metastases, children under 2 years had better survival curves than those over 2 years.