Elevated magnetic field exposures are associated with increased childhood leukaemia risk. A link with breast and other cancers has been postulated via modified melatonin activity. Other illnesses have been linked to electricity distribution, by association or mechanistic considerations. For selected illnesses, this paper estimates the annual number of excess cases that might occur near high-voltage powerlines in the UK. Within 150m of powerlines, magnetic field exposures above 0.1 microT are postulated to result in 9000 excess cases of depression in adults and 60 cases of suicide. Electric field effects can mediate increased exposure to air pollution. Within 400m of powerlines, this may result annually in 200-400 excess cases of lung cancer, 2000-3000 cases of other illnesses associated with air population and 2-6 cases of childhood leukaemia. Seventeen cases of non-melanoma skin cancer might occur by exposure directly under powerlines.