ABSTRACT: In order to examine the accumulation pattern of organotin compounds (OTs) in relation to the migration of diadromous fish, the concentrations of tributyltin (TBT) and triphenyltin (TPT) compounds and their derivatives were determined in the liver tissues of both sea-run (anadromous) and freshwater-resident (nonanadromous) types of the brown trout Salmo trutta. Ontogenic changes in the otolith strontium (Sr) and calcium (Ca) concentrations were examined along the life history transect to discriminate the migration types. The sea-run and freshwater-resident life history styles of S. trutta were found to coexist sympatrically based on the otolith Sr:Ca ratio. The otolith Sr:Ca ratio of sea-run S. trutta fluctuated strongly along the life history transect in accordance with the migration pattern between sea and freshwater. In contrast, the Sr:Ca ratios of freshwater-resident fish remained at constantly low levels throughout the otolith. There were generally no significant correlations between TBT and TPT accumulation and various biological characteristics such as total length (TL), body weight (BW) and sex. It is noteworthy that the TBT and TPT concentrations in sea-run S. trutta were significantly higher than in freshwater-resident individuals, although they are intraspecies. These results suggest that the sea-run S. trutta has a higher ecological risk of TBT and TPT exposure than the freshwater residents during their life history.