This study determined the concentrations of triphenyltin (TPT) and its degradation products, diphenyltin (DPT) and monophenyltin (MPT), in the aquaculture clam Corbicula fluminea and the wild golden apple snail Pomacea canaliculata. Sediments from irrigation ditches and clam aquaculture ponds, and soils from paddy fields were also analysed for these compounds in order to elucidate the sources and impact of phenyltin contamination. Considerably high levels of TPT were found in clams (<5.7–68.7 ng g–1 WW, wet weight), snails (ND (not determined)–1558.0 ng g–1 WW), and soils (ND–336.8 ng g–1 DW, dry weight), but not in sediments. The accumulation of phenyltin compounds in clams and snails was attributed to the spraying of triphenyltin-based pesticides in paddy fields. The higher levels of phenyltins accumulated in snails did not result in higher imposex levels, but caused a longer penis sheath length. The biota-sediment accumulation factor (BSAF) indicated that clams (2.3–6.9) had a higher bioaccumulative ability of TPT from sediments than snails (1.0–1.4). Relatively low levels of the hazard quotients of TPT (i.e. <1) suggested consumption of the aquaculture clam might not have a potential human health risk.