Persistent organochlorines, such as PCBs, DDTs, chlordanes (CHLs), hexachlorocyclohexane (HCHs) and hexachlorobenzene (HCB), polycyclic aromatic hydrocarbons (PAHs) and tributyltin (TBT) were determined in oysters and rock shells collected from coastal waters of the Ariake Sea in 2001. In general, PAHs showed the highest concentration in oysters (average: 1340 ng/g, range: 51-8,300 ng/g lipid wt.), followed by PCBs (average: 530 ng/g, range: 28-2,000 ng/g), DDTs (average: 310 ng/g, range: 37 to 1,000 ng/g), CHLs (average: 190 ng/g, range: 72-450 ng/g), HCHs (average: 22 ng/g, range: 3.1-140 ng/g) and HCB (average: 7.0 ng/g, range: 1.0-20 ng/g). The greater concentrations of PAHs, PCBs and HCHs were found in oysters from the Omuta River, implying the occurrence of potential sources of these contaminants in this river. A positive correlation was found between TBT concentrations and RPL (Relative Penis Length) Index in rock shells, suggesting that TBT has induced an imposex in gastropods, even though the use of TBT has been banned in Japan for more than ten years.