This review summarizes reported biological effects of extremely low frequency (ELF) electric and magnetic fields, describing them as significant and often acting as stressors. Reported outcomes include metabolic, hormonal, and body weight changes in rodents, lethality at high exposure levels in mice and insects, and increased mitotic index in mouse tissues/cells under specified exposure conditions. The review suggests many effects may be mediated through neuroendocrine, nervous system, or behavioral responses to field exposure.