Three groups of ICR male and female mice were exposed to 50-Hz, sinusoidal, alternating, horizontal magnetic fields of 0.0 mT (sham), 0.5 mT and 5.0 mT (rms) for 9 and 2 weeks prior to mating for males and females, respectively, through fertilization and until cesarean sectioning. Fetuses were collected by cesarean section on the 18th day of gestation. Approximately half were randomly selected for skeletal examination and the remainder used for visceral examination. No significant differences were found between the field- and the sham-exposed groups in pre-, post- and total implantation losses; number of live fetuses; sex ratio; live fetal weight; number of externally abnormal fetuses; and numbers of fetuses with skeletal and visceral anomalies. These results suggest that exposure to power-frequency magnetic fields has no major effects on reproduction and development in mice, and do not support the association of EMF exposure with adverse reproductive effects suggested by epidemiology.