This study assessed potential human health risks posed by tributyltin in seafood purchased from U.S. seafood markets. In 1989 and 1990, samples of fish, bivalve molluscs and crustacea were purchased at local markets along the Atlantic, Gulf and Pacific coasts of the United States and along the Great Lakes (Lake Michigan). Samples were then analyzed for tributyltin, and the concentrations observed used to evaluate potential human health risks from consumption of market-bought seafood on the basis of available mammalian toxicology data. The assessment indicated health effects were unlikely from exposure to tributyltin in market-bought seafood during 1989 to 1990, shortly after peak tributyltin usage in antifoulant bottom paints on vessels in the United States.