Adult primary tumors of the central nervous system are rare, but the incidence is increased in some European countries. Several environmental exposures have been investigated as potential risk factors, but for most, scientific evidence is still lacking. Here we review studies of environmental factors potentially involved in the carcinogenesis of brain tumors: the potential association between primary central nervous system tumors and ionizing radiation, some toxic agents (N-nitroso compounds, pesticides), air pollution, and radiofrequency electromagnetic waves. Brain-ionizing irradiation, especially during childhood, constitutes a well-established risk factor for brain tumors. Exposure to environmental toxins has been poorly explored and data give inconsistent clues about N-nitroso compounds or pesticides as risk factors of brain tumors even for prenatal exposure. For out-door pollution and risk of brain tumour, results of large prospective studies are contradictory. The effect of mobile phones on the risk of developing brain tumors has not been established for glioma and meningioma in adults, but the link with acoustic neurinoma is becoming robust. The effect of mobile phones has still not been explored in children.