In the present study the levels of the organotin compounds were determined in fish and shellfish which were purchased from retail markets in Niigata, Japan. The concentrations of dibutyltin (DBT), tributyltin (TBT), diphenyltin (DPT) and triphenyltin (TPT) compounds were separately determined by FPD-gas chromatography. Eight species (yellowtail, tuna, cuttlefish, olive flounder, northern shrimp, cinnamon flounder, Japanese sea bass and oyster) were studied and five samples of each species were analyzed in each season, which meant 40 samples in one season, and 160 in total. Among the compounds of interest, DBT, TBT and TPT were detected. The highest concentrations detected were 0.674 microgram/g for DBT, 0.669 microgram/g for TBT and 0.186 microgram/g for TPT. DBT was detected as much as TBT, however, its concentration was not correlated with that of TBT. Seasonal changes of the mean value of the concentration of DBT and TBT were observed. In some species, such as yellowtail and Japanese sea bass, combined contaminations of these organotin compounds were also evident. This study is the first step to elucidate possible health hazards by environmental pollution of organotin compounds on human beings.