In electric utility workers, occupational exposure to magnetic fields has previously been associated with mortality from acute myocardial infarction (AMI) and arrhythmia but not from chronic coronary heart disease (CCHD) or atherosclerosis. To investigate these health endpoints further, the authors examined mortality from AMI (n = 407) and CCHD (n = 369) in a cohort of 35,391 male workers at the Southern California Edison Company between 1960 and 1992. Exposure was estimated according to duration of employment in occupations associated with high levels of magnetic field exposure and was calculated as cumulative exposure to magnetic fields expressed in micro-Tesla-years. Adjustment was made for age, calendar time, socioeconomic status, race, and worker status (active or inactive). The authors found that men working longer in high-exposure occupations or working as electricians, linemen, or power plant operators had no increased risk of dying from either AMI or CCHD compared with men who never worked in high-exposure occupations. For cumulative exposure, no association was observed with mortality from AMI (rate ratio per 1 micro T-year = 1.01, 95% confidence interval: 0.99, 1.02) or CCHD (rate ratio per 1 micro T-year = 1.00, 95% confidence interval: 0.99, 1.02). These results, indicating no exposure-related risk increase for AMI mortality, do not confirm previous results.