The aquatic chemistry, fate and toxicity of tributyltin are reviewed. A summary is given of investigations of the occurrence and persistence of tributyltin and its less toxic degradation products in water and sediment in Canada. Tributyltin was mainly found in areas of heavy boating or shipping traffic, which was consistent with its use as an antifouling agent. In about 8% of the 269 locations across Canada at which samples were collected, tributyltin was found in water at concentrations which could cause chronic toxicity in a sensitive species, rainbow trout. Tributyltin was occasionally found in the surface microlayer of fresh water at much higher concentrations than in subsurface water. It was also found in about 30% of sediment samples collected across Canada. The few fish analyzed that contained tributyltin were from harbours, a finding consistent with findings in water and sediment. Biological degradation in water and sediment appears to be the most important factor limiting the persistence of tributyltin in aquatic ecosystems. Estimates of the half-life of biological degradation of tributyltin in fresh water and sediment in Canada are in the range of a few weeks to 4-5 months, respectively. Recent Canadian regulations of tributyltin are discussed as well as the current Canadian Environmental Protection Act review of non-pesticidal organotins.