Twenty-four hours after the administration of Ga-67 citrate and Fe-59 citrate, rabbits were killed and their livers removed and homogenized. Labile proteins in the filtered liver homogenates were denatured; ferritin was then crystallized from the supernatants by cadmium sulfate. Sephadex G-200 gel filtration of the ferritin fractions was done to determine the distribution of molecular weights in the substances associated with Ga-67 and Fe-59. It was found that Ga-67 was incorporated into the crystallizable ferritin fraction of rabbit hepatocytes with approximately one-sixth the uptake of simultaneously administered Fe-59. Gel-filtration chromatography confirmed that both the Ga-67 and the Fe-59 of the crystallizable ferritin fraction were associated with substances of the appropriate molecular weight for ferritin.