Low dose (10mg/kg as rare earth elements) or high dose (50 mg/kg as rare earth elements) of 4 kinds of rare earth element solutions, i. e. dysprosium chloride (DyCl3), europium chloride (EuCl3), ytterbium chloride (YbCl3) and yttrium chloride (YCl3), were administered intravenously from the caudal vein of rat, and the distribution and the histological change in the tissues were investigated at the 8th days after the administration. The rusults were as follows : 1) The administered rare earth elements were mainly accumulated in the liver, spleen and bone. The concentrations of rare earth elements in the kidney, pancreas and heart were low. No rare earth elements was detected from the muscle and whole blood. 2) More than 3 times of amounts of the rare earth elements were accumulated in the spleen of rats when administered low dose of YCl3, and higher amounts of the rare earth elements were accumulated in the bone of the rats administered YbCl3 compared to the rats administered other rare earth elements of low dose. On the contrary, the difference in the pattern of accumulation in the various organs was not observed when administered high dose. The distribution (% of dose) of the rare earth elements in the spleen tended to elevate but those in the bone tended to be lower in the bone of the rats administered high dose. 3) No obvious change was observed in the liver of the rat administered low dose. The deposition of the brown substance or xenobiotics was observed in the spleens of the rats administered low dose of DyCl3 and YCl3. The reaction of macrophage was observed in the spleen of the rats administered low dose of YCl3. 4) The formation of xenobiotic glanuloma was observed in the spleen when the rats administered high dose of rare earth elements. Therefore, when the chlorides of Dy, Eu, Yb and Y were administered to the rats intravenously, the administered rare earth elements accumulated mainly in the liver, spleen and bone and the formation of glanuloma was observed in the spleen when high dose administered.
