An assessment of the environmental chemistry and toxicology of organotins, emphasizing trialkyltins, is presented to respond to a State of North Carolina, Division of Environmental Management proposal which purports to ban the discharge of organotins into state surface waters. The assessment relies upon a comprehensive evaluation of both published and unpublished scientific literature to establish the current state of knowledge concerning these compounds. This is followed by a critique of the State's proposal and a counterproposal, including recommendations for further investigations of the environ- mental chemistry and toxicology of these compounds. Some organotins used commercially because of their biocidal properties are susceptible to a number of naturally occurring processes that tend to reduce their concentrations and render them biologically unavailable after they are discharged to aquatic environments. The most important processes are sorption to particulates, photo1ysis, and biodegradation, the latter occurring not only in bacteria, but also in algae, fish and mammals. Trialky1tins are used commercially because of their excellent biocidal properties, and indeed they have relatively high acute and chronic toxicities to some species of aquatic life. However, toxicity data need to be considered hand-in-hand with data on what concentrations prevail in state waters, whether the organotins in surface waters exist in forms that can cause harm, and whether the organotins are harming the fish and wildlife living in these waters. The moderately elevated rate by which some aquatic species acquire (i.e., bioconcentrate) trialky1tins are balanced by the ability of aquatic life and mammals to metabolize the compounds and cleanse themselves of the materials when they enter uncontaminated water. The biological detoxification and depuration mechanisms appear to virtually eliminate the threat of biomagnification.