This report presents data on the distribution of 8,612 cases of primary tumors of the brain, cranial nerves and cranial meninges (both benign and malignant) diagnosed among residents of Los Angeles County from 1972 to 1985. Incidence rates of gliomas, meningiomas, nerve sheath tumors and all histologic types combined are presented for specific age, sex and ethnic groups. At all ages, the highest incidence is seen for gliomas among men. Meningioma rates are higher among women than men in every ethnic group. In both sexes, glioma rates are highest among whites, and meningioma rates are highest among blacks. Asians have the lowest rates of both types of tumors. Proportional incidence ratios are elevated among those born in Eastern Europe, Southern Europe and the Middle East and among Jewish residents of Los Angeles County. A clear trend of increasing glioma incidence with increasing social class is seen among males. An analysis among white men aged 25-64 by occupation and industry at the time of diagnosis supports several previously published findings. A glioma excess is evident among workers in the aircraft industry. Workers in the petroleum industry and the rubber and plastics industry have an excess of meningiomas. Occupational groups at excess risk include dentists who have an increased risk of all types of brain tumors and electricians whose excess risk is limited to gliomas.