Radiographs of the left forelimb were obtained after slaughter in 16 14-month-old pigs. From age 8-14 months, eight pigs in the experimental group received 2 mg F-/kg body weight per day. Bone maturity in F-animals was the same as in controls. Cortical thickness was increased by 10 per cent in the fluorotic animals (p less than 0.01) and their plasma-fluoride levels increased throughout the experimental period to approximate those reported for man in endemic fluorosis areas. Thus fluoride given in the dose used and over that period, did not affect maturation in the long bones but increased cortical bone mass in the diaphyses.