Adult mated female Wistar rats (200-250 g) were obtained from the Experimental Animal Center of Bejing University, Bejing, China. They were randomly divided into 4 groups of 10 each. The groups ingested ad libitum fluorinated drinking water (5, 15, 50 ppm F^- ) or distilled water for about 60 days during their gestation and lactation starting from the day of mating. Their offspring drank fluorinated water freely following maternal lactation till the 80th day after birth.