The possible deleterious effects on human health due to exposure to the 50-60 Hz electromagnetic fields of power lines have been of concern for over 30 years. This important problem in biophysics has recently generated much activity. In the following sections of this article, the validity of the physical principles that underlie the reasoning and conclusions in previous articles is examined in the light of recent research work. Important misconceptions, errors, and omissions are pointed out. Topics covered include: natural sources of exposure; exposure to 60 Hz electromagnetic fields; thermal noise; epidemiological studies; and electric and magnetic fields in houses.