An exploratory case-control study was conducted in 15 hospitals in the Baltimore, MD, SMSA of possible etiologic factors associated with brain tumors in children. Eighty-four children with brain tumors were compared to normal children and to children with other malignancies. Parents of these children were interviewed about a variety of possible etiologic factors. The findings Included: 1) children with brain tumors as well as children with other cancers had a greater tendency than normal children to have been first births and to have had higher birth weights; 2) more children with brain tumors had a sibling with epilepsy or seizures than did normal children, and several of the mothers of children with brain tumors had themselves had epilepsy or a stroke at a relatively young age; 3) there were no significant differences between the groups with regard to several maternal characteristics, including smoking during pregnancy and prior radiation exposure; 4) more children with brain tumors and children with other cancers were found to have had exposures to insecticides than had normal children; 5) fewer children with brain tumors or with other cancers were reported to have had tonsillectomies than normal children; and 6) more of the children with brain tumors as well as the children with other malignancies were reported to have been exposed to farm animals and to sick pets. This exploratory study is one of the first case-control studies of the epidemiology of brain tumors in children, and the results suggest directions for future epidemiologic studies In this relatively uncharted field.