Health risks of power-frequency electric and magnetic fields (EMF) in the generation and transmission of electric power were investigated in a program comprising nine separate projects. The central objectives were to assess the practical importance of electric and magnetic field exposure as a health risk, to produce data applicable to field management measures at a major power company, and to support and spur research activities on electric and magnetic fields as environmental agents. Electric and magnetic fields seemed to be weak environmental factors, but the findings were uncertain and controversial as to the health risks except that, electric field strengths (about 1.5 kV.m-1) found even in the vicinity of 110 kV power lines may cause interference with cardiac pacemakers. There is still a need, however, for further basic research focused on the interaction mechanisms of electric and magnetic fields and biological tissue.