In mice given a single intravenous injection of 2.6 uCi of monomeric 239Pu (IV) per kilogram, 30% was in the bone from 6 to 90 days, and 21% at 300 days; 82% of the mice had at least 1 malignant bone tumor at death. In a 2nd group receiving the Ca form of diethylenetriaminepentaacetic acid (DTPA) daily for 12 days, beginning 3 days after Pu, the skeletal Pu was reduced to 14% of the injected amount, and the final tumor incidence was 75%. In a 3rd group, in which DTPA treatment was initiated 1 hour after Pu, the skeletal burden was reduced to 7% of the injected amount, and the final tumor incidence was 60%. Only 1% of DTPA-control mice had a bone tumor. Average survival times after injection in these 4 groups were 361, 450, 556, and 650 days. The death rate of mice with bone tumors increased both with age and with time elapsed after Pu; it decreased with decreasing Pu concentration in bone after DTPA. DTPA removed approximately equal fractions of Pu from all bones. Of all the bones, the Pu concentration in the femur most closely represented the skeletal average. Monomeric Pu was more carcinogenic in bone than an equal concentration of polymeric Pu, probably because of differences in microscopic localization.