Summary The metabolic fate of perfluorooctanoic acid administered by stomach intubation to female rats was investigated. The nonionic fluorine level in the serum was increased 200-fold after administration of the dose but returned to baseline levels by 52.5 hr. Although perfluorooctanoic acid is rapidly absorbed and bound to nonultrafilterable components in the serum, the entire dose of nonionic fluorine was recovered in the urine and feces after 96 hr. Neither the ionic fluoride level in the serum nor the rate of ionic fluoride excretion in the urine was significantly altered by the administration of perfluorooctanoic acid. Although perfluorooctanoic acid has not been identified in the urine, the available data suggest that it has been excreted intact or in possibly conjugated form.