Perfluorooctanoic acid (PFOA) is an octanoic acid derivative to which all aliphatic hydrocarbons are substituted by fluorine. PFOA and its salts are commercially used in various industrial processes. The chemical is persistent in the environment and does not undergo biotransformation. It was reported that PFOA is found not only in the serum of occupationally exposed workers but also general populations. Recent studies have suggested that the biological half-life of PFOA in humans is 4.37 years based on study of occupationally exposed workers. It is increasingly suspect that PFOA accumulates and affects human health, although the toxicokinetics of PFOA in humans remain unclear. In experimental animals, PFOA seems low in toxicity. PFOA is well-absorbed following oral and inhalation exposure, and to a lesser extent following dermal exposure. Once absorbed in the body, it distributes predominantly to the liver and plasma, and to a lesser extent the kidney and lungs. PFOA is excreted in both urine and feces. Biological half-life of PFOA is quite different between species and sexes and the difference is due mainly to the difference in renal clearance. In rats, renal clearance of PFOA is regulated by sex hormones, especially testosterone. PFOA is excreted into urine by active tubular secretion, and certain organic anion transporters are thought to be responsible for the secretion. Fecal excretion is also important in the elimination of PFOA. There is evidence that PFOA undergoes enterohepatic circulation resulting in reduced amounts of fecal excretion. Elucidation of the mechanisms of transport in biological systems leads to elimination and detoxification of this chemical in the human body.