Many of the studies in which animals or cells have been exposed at various frequencies and intensities of NER radiation have reported inconsistent and transient changes in the functional integrity of the immune defense system. Many of the reported immune effects of NER, however, appear to result from a generalized stress response which is due to NER-induced heating. The absence of increases in core temperature following NER does not preclude a thermal interaction that the animal is able to compensate for and control. Conclusions of the human health implication of observed interactions of NER with the immune system in experimental models must be made most cautiously. There is presently no convincing evidence from in vitro or in vivo studies for adverse alterations in the immune system at NER radiation intensities comparable to average environmental levels, i.e., 0.01 to 0.1 microwatts/cm2 in the frequency range of 54 to 900 MHz, which encompasses the resonant frequency for humans.