The Computerized Risk And Bioaccumulation System (CRABS, Version 1.0) is an expert system that predicts tissue residues of fifteen neutral organic pollutants in sediment-dwelling organisms and the human cancer risk from consumption of the contaminated shellfish. Bioaccumulation from bedded sediment can be predicted from the thermodynamic partitioning, first-order kinetic, or toxicokinetic model. All the models can predict steady-state tissue residues while the two kinetic models can predict non-steady-state uptake or elimination. CRABS then predicts the lifetime human cancer risk from consumption of clams and other non-mobile sediment-dwelling organisms containing the predicted (or measured) tissue residue. The linearized multistage model is used to predict cancer risk for a single pollutant from a single species diet. The program guides the user in estimating shellfish consumption rates if no site-specific rates are available. CRABS is designed to promote thorough documentation of the assumptions and data as well as to error check the entered values.