The potential for the medical uses of EMFs is still in its very early stages of understanding. What may be useful at one level of field strength or range of frequencies may not be at others. The research available will at least guide us in terms of what is currently known. Because of the very basic actions of EMFs on biology, it is possible that most EMFs will have broad ranges of possible actions, beyond the research evidence available. Tolerance and safety limits of EMFs are fairly well understood and there is likely little risk if these limits are not exceeded. The radiofrequency fields, that produce heating, and the strong fields, that affect medical equipment, should clearly be used in the appropriate circumstances.