Fluoride as a supplement can affect the structural integrity of bone. Fluoride that is incorporated in the mineral, substitutes for the hydroxyl group producing hydroxyfluorapatite crystals and presumed to increase bone strength by preventing resorption. Because of this, fluoride therapy has been carried out in clinical trials for the treatment of osteoporosis. Although fluoride renders the mineralized tissues resistant to resorption, the effects of fluoride on bone strength and cortical bone mass specially that of the developing bone has not yet been characterized. The purpose of the study was to analyze the effect of fluoride on developing teeth and bone in young rats through histomorphometry. Sixteen wistar rats were used and divided into two groups; non-fluoride supplemented (control) and fluoride-supplemented groups. Four weeks after, the rats were sacrificed and the mandible and femur were subjected to histological and histomorphometric analyses. No clinical difference was observed between the two groups. The amount of mineralized cartilage was higher in fluoride-supplemented group compared to the control group. However, the amount of new bone was lesser in fluoride-supplemented group compared to the control group. This histomorphometric analysis showed that during endochondral ossification, 10 ppm fluoride administration caused some changes in calcified cartilage and bone mineralization in young rats.