The metabolism of polonium (7440086) was studied in baboons. Six adult female baboons (Papio-anubis) were injected with 8.14 to 29.6 becquerels per kilogram (Bq/kg) polonium-210 (13981527) (Po210) as polonium-citrate. Urine and feces samples were collected daily from two baboons given 28.9 and 29.6Bq/kg for 91 and 30 days, respectively, and analyzed for Po210. The baboons were killed 1, 7, 14, 30, 80, or 91 days after dosing to determine the tissue distribution of Po210. Urinary and fecal excretion of Po210 activity could be described by a single exponential function with biological halflives of 15.6 and 14.5 days, respectively. Cumulative urinary and fecal excretion of Po210 amounted to 37.7 and 55.1% of the injected doses, respectively. Po210 accumulated primarily in the liver, blood, gastrointestinal tract, kidney, spleen, skeleton, and musculature. The retention of Po210 activity in the tissues could also be described by single exponential functions with biological halflives ranging from 15.4 days in the liver to 33.8 days in the skeleton. Po210 was cleared from the blood with halflives of 8 to 19 days; however, there was an initial rapid phase with a halflife of 38.7 minutes. The authors conclude that these data support previous studies which found that Po210 is a soft tissue seeker. Excretion fractions, however, differ significantly from those found in other species.