All 1632 cases of meningioma reported to the Norwegian Cancer Registry from 1955 to 1986 have been studied: a) 96% appeared in patients over 30 years of age, b) 95% were histologically benign, c) 88% were located intracranially, and d) 66% occurred in females. The female predominance manifested itself in the middle age period. Eighty-seven percent of the intraspinal meningiomas presented in females, but the ratio between intracranial and intraspinal meningiomas was significantly lower in females (5.4) than in males (20.4). Increased incidence rates of meningioma in females are revealed for the birth-cohorts after 1930. The reason for this change is unclear so both environmental and hormonal factors should be explored. Based upon the epidemiological data, it appears that female sex hormone(s) could act as a growth stimulus in the development of meningiomas, but are neither sufficient nor necessary for tumourigenesis.