A method for the determination of cadmium in rat femur by flameless atomic absorption spectrophotometry was studied. The solution obtained by digestion of the bone with nitric acid and perchloric acid was applied to the Dowex 50 W×8 column, and cadmium was selectively isolated from calcium, phosphorus, and other elements contained in the bone by elution with 0.5N hydrochloric acid. This isolated cadmium was determined using the flameless atomic absorption spectrophotometer. The recovery of cadmium added to 1 g of commercial bone powder by this procedure was 98.0-116.5%, and good recovery of cadmium was also obtained in the range of 0.1-2.0 g of sample weight of the bone. By using this procedure, the content of cadmium in femur of male Wistar strain rats without artificial exposure to cadmium was determined, and the values were in the range of 0.03-0.08 ppm, and the avarage of 0.06 ppm in the bone.