Reduced male proportion in offspring of male carbon setters prompted a study into whether offspring of workers exposed to strong static and extremely low-frequency electromagnetic fields (ELF) had a deviant sex ratio. The study was based on all births in Norway 1970-1993. The reference population was offspring of parents not exposed to ELF. The male proportion in offspring of men in aluminum works was 50.38%, RR 0.98 (0.94-1.03), in manganese works 47.32%, RR 0.92 (0.83-1.02), in factories producing iron 50.03%, RR 0.97 (0.93-1.02), in nickel works 48.27%, RR 0.94 (0.84-1.05), and in electric wire production 47.20%, RR 0.92 (0.80-1.05). In the offspring of women in aluminum works, the male proportion was 37.04%, RR 0.72 (0.59-0.90), in all smelter works grouped together, 45.13%, RR 0.88 (0.79-0.99). The male proportion in the reference population was 51.42%. The male proportion in offspring of men in industries with ELF, was slightly reduced, while offspring of women was significantly reduced.