Abstract Concentrations of butyltin compounds including tributyltin (TBT), dibutyltin (DBT) and monobutyltin (MBT) were determined in mollusc samples from Chinese Bohai coastal sites to evaluate the extent of contamination and potential adverse effects on health. Wide existence of butyltins was found in these samples with a detection rate of up to 90%, and the concentrations of the total butyltin (∑BTs: TBT + DBT + MBT) ranged from <2.5 to 397.6 ng Sn/g wet weight (mean 63 ng Sn/g). Among BTs, TBT was the predominant compound in most of the samples, indicating ongoing usage of TBT-based antifouling agents in China. The different accumulation capabilities of BTs among various species were studied. The wide occurrence and serious pollution of BTs in seafood indicated a potential danger for the health of the local people who cared for these foods.