Osteofluorosis was induced in rabbits by the ingestion of 500 ppm F in their drinking water over a period of 30 days. The tibiae from experimental and control animals were selected for macroscopic, microscopic and microradiographic observation. Transverse sections of 100 mum thickness were prepared for an electron-microprobe analysis to determine Ca, P and F concentrations and to display the topographical distribution of F as revealed by the X-ray image of its Kalpha1 radiation. Variation in amount of periosteal and endosteal deposition was observed along the length of the bone. Changes, including numerous mottled osteones, were seen in the compact zone of bone which had been formed prior to the start of the experiment. The Ca/P ratio appeared to show a variation related to the F concentration.