Since 1979 several studies have been published that suggest that residential exposure to electromagnetic fields could increase the risk of childhood cancer. Such studies have also been published for adults. In addition there are several studies suggesting that people in "electrical" occupations are at an increased risk of cancer. The objective of this review was to determine whether the role of electromagnetic fields in the origin of cancer can be established from the epidemiologic literature. Several of the studies suffer from methodological or other shortcomings, but it is not clear whether these problems are likely to explain the results. No conclusion can be drawn about the role of electromagnetic fields in the origin of cancer on the basis of current data. The existing literature, however, strongly suggests that research in this area should be pursued.