In order to find the mercury content levels in normal maternal body and newborns, total mercury and methylmercury contents in maternal blood, hair, placenta, umbilical cord, and umbilical cord blood (newborn blood) were examined. In 89 normal women after delivery, living in Nagoya City, the following results were obtained. Total mercury and methylmercury contents were 1.83±0.91 and 0.93±0.56 μg/100g, respectively, in maternal blood, 2.57±1.03 and 1.77±0.72 ppm, respectively, in mother's hair, 9.07±9.34 and 1.07±0.96 μg/100g, respectively, in placenta, 2.36±2.89 and 0.72±0.54 μg/100g, respectively, in umbilical cord, and 2.67±1.20 and 1.56±0.95 μg/100g, respectively, in umbilical cord blood. Both total and methyl-mercury contents in umbilical cord blood (newborn blood) were apparently higher than in maternal blood, and it seems that mercury compounds transfer through placenta to the fetus and accumulate there.