The 1957-1958 incidence of neoplasms among the survivors of the Hiroshima A-bomb, varies directly with radiation dose insofar as it may be inferred from distance from the hypocenter at exposure. The incidence of all malignant neoplasms among the survivors who were within 1000 meters is more than 4 times that of the non-exposed population. The incidence of benign neoplasms among the survivors exposed within 1500 meters is also significantly higher than that among the non-exposed. For survivors under 1500 meters significant differences are seen between the numbers of observed cancers of the lung, stomach, uterus and ovary and the expected cases calculated from the age-specific rates of the non-exposed portion of the Hiroshima population. The increased incidence among survivors within 1500 meters is not related to sex or age. 18 references, 2 figures, 14 tables.