24 recently weaned Sprague‐Dawley rats were divided equally into 3 groups and given distilled drinking waterad libitumcontaining 0, 1 or 5 ppm F‐ (as NaF), respectively. Among the 13 animals that received the fluoridated water and survived the 2‐year experimental period, 4 developed macroradiographically demonstrable resorption cavities in their femurs. Three of these animals belonged to the 1 ppm group. No resorption cavities were seen in the 6 surviving, control rats. There was no sign of tooth changes, especially no striated depigmentation of the enamel of the inc