Accumulation of tributyltin (TBT) in serum, liver and muscle of olive flounder (Paralichtys olivaceus) was investigated in a 60-d static renewal exposure at $0.1{mu}g$ TBT/L. Tributyltin accumulated rapidly from 83 ng Sn/g to 2,227 ng Sn/g on a wet weight basis in the serum of the olive flounder and to a greater extent than in the other tissues. The accumulated TBT concentrations in tissues were in the order of serum>liver>muscle on wet or dry-weight basis. High concentrations of dibutyltin (DBT: 990 ng Sn/g dry wt) and monobutyltin (MBT: 141 ng Sn/g dry wt), degradation products of TBT were found in liver of olive flounder at the end of exposure. On the other hand, DBT and MBT was below the detection limits in muscle during the exposure, and only low concentration of DBT (56 ng Sn/g) were detectefd in serum. Butyltin compounds were also quantitatively determined in feral fine-spotted flounder (Pleuronichthys cornutus) collected from Gwangyang Bay as one of polluted area and Sori Island as a reference site. All three butyltin compounds were detected from the fine-spotted flounder from Gwangyang Bay up to 3,107 ng Sn/g of total butyltins in liver, while 120 ng Sn/g of total butyltin concentration was found in the liver of fish from Sori Island.