Since the atomic bomb explosions in Hiroshima and Nagasaki, high incidences of 
leukemia, thyroid cancer and other tumors have been reported as atomic 
bomb-induced tumors. We investigated the incidence of meningioma among Hiroshima 
atomic bomb survivors. Sixty-eight patients surgically treated for meningioma 
who had been within 2.0 km of the hypocenter of the explosion were identified. 
Six hundred and seven non-exposed patients with meningioma were also studied. 
Treatment dates were from 1975 to 1992. The incidences of meningioma among 68 
subjects within 2.0 km and 607 non-exposed patients were 8.7 and 3.0 cases per 
10(5) persons per year, respectively. The incidences of meningioma among the 
survivors of Hiroshima in 5-year intervals since 1975 were 5.3, 7.4, 10.1, and 
14.9, respectively. The incidences of meningioma classified by distances from 
the hypocenter of 1.5-2.0 km, 1.0-1.5 km and less than 1.0 km were 6.3, 7.6 and 
20.0, respectively. The incidences of meningioma classified by doses to the 
brain of 0-0.099 Sv, 0.1-0.99 Sv and more than 1.0 Sv were 7.7, 9.2 and 18.2, 
respectively. The incidence of meningioma among Hiroshima atomic bomb survivors 
has increased since 1975. There was a significant correlation between the 
incidence and the dose of radiation to the brain. The present findings strongly 
suggest that meningioma is one of the tumors induced by atomic bombing in 
Hiroshima.