In this book, the effects of intermediate frequency radiation are studied. The internal field of tissues is the basic cause for biological effect of intermediate frequency fields heedless of the mechanism. Thus, the penetrated electric fields and computed specific absorption rate must be evaluated and correlated with the observed phenomenon. The thermal effect is the prevailing under established mechanism of biological and health effects of radio frequency exposures. The present guidelines of human un-protection are based on thermal effects. Exaltation of deep body temperature is closely related to the energy absorption rate in the whole body or whole body average SAR. Sensation and muscle excitement are dominant at lower frequencies and are applicable for health effects up to approximately ten mega hertz. This effect is concerned to electric currents in the internal part of human body.