Above-average exposure to electromagnetic fields has been associated with certain nonmalignant medical conditions such as amyotrophic lateral sclerosis, other neurologic diseases, depressive symptoms, and suicide. The authors conducted a nationwide mortality study in Denmark of 21,236 men employed in utility companies between 1900 and 1993. The causes of death were ascertained for January 1, 1974, through December 31, 1993, and cause-specific mortality was analyzed by latency and estimated levels of exposure to 50-Hz electromagnetic fields. Overall, 3,540 deaths were observed as compared with 3,709 expected from national mortality rates, yielding a standardized mortality ratio of 0.96 (95% confidence interval 0.93-0.99). A slight excess in mortality from cancer was due to deaths from cancers of the lung and pleural cavity, probably because of exposure to asbestos. A twofold increase in mortality from amyotrophic lateral sclerosis and a tenfold increase in mortality from electrical accidents were seen on the basis of 14 and 10 deaths, respectively, the former increasing with time since first employment in a utility company. The excess mortality from amyotrophic lateral sclerosis seems to be associated with above-average levels of exposure to electromagnetic fields and may be due to repeated episodes with electric shocks.