The possible health effects of electro-magnetic (EMF) from high-voltage electric power lines have been discussed sine the 1970s. The concern was triggered by epidemilogical studies in the United States and Europe that suggested a slightly increased incidence of leukaemia's and brain tumours occured among those living and working near high-voltage power lines. Although studies can indicate an associate between factor and effect, the studies themselves cannot confirm a cause-effect relationship. Whether EMF is producing these ill effects must be confirmed by experimental studies. This text hopes to provide understanding of the concern about EMF exposure and the adverse effect they may have on the public.