The contents of total and methyl mercury in scalp hair samples of 1179 fishermen living at a typical Hg-polluted region in Northeast China and 27 lying-in women and their new born babies in Beijing have been determined by instrumental neutron activation analysis, gas chromatography (electron coupling) and other techniques. Only 18 of all fishermen have the Hg contents above 5 µg/g, which indicates that the Hg pollution there has been substantially alleviated. The longitudinal Hg patterns of the lying-in women show a gradually lowering tendency during pregnant period. Further, the Hg contents of the new-born babies are generally above or close to those of their mothers, confirming the mechanism that the methyl Hg, an organic species of Hg with high toxicity, is readily able to penetrate the placental barrier and accumulated in fetus. Thus, the mercury poison has occurred at the early stage of pregnancy.