Butyl- and phenyltin residues in bivalves were quantified around the coast of Korean peninsula in 1995-1998 and 2001. Butyltin compounds were detected at all the sites surveyed, whereas phenyltins were detected at 41 out of 67 sites in 1995-1998. Tributyltin (TBT) concentrations in bivalves ranged 48-2800 ng Sn/g on dry weight basis. Triphenyltin (TPT) concentrations ranged <3-1820. The mean TPT concentration was 3.5 times less than that of TBT. Spatial distribution of TBT was closely related to boating and dry-docking activities. TPT concentration in bivalves showed significant correlation with TBT. Concentrations of TBT in bivalves, 2001 are not significantly changed compared to those in 1995-1998. However, TPT concentrations in bivalves steeply decreased in 2001. High concentration of TBT and lesser extent TPT and their nation-wide distribution indicate that organotins are one of major organic pollutants in the marine environment of Korea.