The brains of rats injected intravenously with 65ZnCl2 or 54MnCl2 were subjected to high resolution autoradiography. 65Zn and 54Mn were largely concentrated in choroid plexus 1 h after injection and then gradually decreased, with increases in other brain regions, suggesting that both metals were taken up gradually into brain mainly via cerebrospinal fluid in the choroid plexus. By 3 days after injection, relatively high level of 65Zn was seen in the dentate gyrus and CA3 region of the hippocampus and in the cerebral cortex. The level of 54Mn was also high in the former, while relatively low in the latter.