Brain tumours are of different cell types, the commonest being tumours of glia called gliomas. Many etiological factors of gliomas have been suggested and certain industries have been implicated. Several epidemiological studies have Linked electromagnetic fields (EMFs) to gliomas. Health effects of EMFs have been studied, both in humans and in experimental animals, mainly with negative findings. Positive experimental evidence linking EMFs to tumours is the effect of EMFs on melatonin production by the pineal gland. Removal of the pineal gland in rats increases the incidence of tumours. Further epidemiological and experimental evidence is required to elucidate this possible link between EMFs and brain tumours. (C) 1994 Wiley-Liss, Inc.