Three studies were conducted to provide information on the biological fate, distribution of radiation doses among tissues, and implications for potential health consequences of an inhalation exposure to mixed-oxide nuclear fuel materials. In each study, Fischer-344 rats, beagle dogs, and cynomolgus monkeys inhaled one of three aerosols: 750{degrees}C calcined mixed oxides of UO{sub 2} and PuO{sub 2}, 1750{degrees}C sintered (U,Pu)O{sub 2}, or 850{degrees}C calcined {open_quotes}pure{close_quotes} PuO{sub 2}. These materials were collected from glove-box enclosures immediately after industrial processing of mixed-oxide fuel materials. Lung retention, tissue distribution, and mode of excretion of {sup 238-240}Pu, {sup 241}Am, and uranium (when present) were quantified by radiochemical analysis of tissue and excreta samples from animals sacrificed at selected times to 6.5 yr after inhalation exposure.