Considers whether power-frequency (60 Hz) electromagnetic fields can significantly affect human health. The problem of estimating the dose in studying this question is discussed. Attention is given to the mechanisms that have been proposed to explain how 60-Hz fields affect biological systems. The results of a study carried out to determine the public perception of the risks are presented. Finally, it is noted that if, on the basis of health-effects evidence, a decision is made to limit human exposure to 60-Hz fields, the first step is to define dose. If dose is measured as the time integral of all 60-Hz electric fields to which humans are exposed, attention would be focused on electric appliances and local wiring. If, on the other hand, only strong 60-Hz electric fields are significant contributors to dose, then exposures to transmission-line fields would warrant primary attention.