Data from urinalyses at ages 9 to 16 were tabulated for children exposed to ionizing radiation in utero at the time of the atomic bombs in Hiroshima and Nagasaki in 1945 and for comparable control groups. Proteinuria was detected more often at various ages in boys in Hiroshima and girls in both cities whose mothers were within 1500 m of the bomb hypocenters. However, the differences were statistically significant only in girls ages 13 or 14. Casts were also seen more commonly in Hiroshima girls located at the same distance. Red and white blood cell excretion in the urine and glycosuria did not appear to be related to radiation exposure. Future investigations will be necessary to define the biological significance of these findings. 11 references, 8 tables.