This report describes the theoretical development, parameterization, and application software of the BASSBioaccumulation and Aquatic System Simulator. This generalized, community-based simulation model is designed to predict the population and bioaccumulation dynamics of age-structured fish communities exposed to hydrophobic organic chemicals and class B and borderline metals that complex with sulfhydryl groups (e.g., cadmium, copper, lead, mercury, nickel, silver, and zinc). This report is not a case study on the application of BASS but a reference and user’s guide. The intended audience of this report and associated software includes research fisheries ecologists, bioaccumulation researchers, and EPA environmental scientists and ecologists who must routinely analyze and estimate bioaccumulation of chemicals in fish for ecological or human health exposure assessments.You may need Adobe Reader to view files on this page. See EPA’s About PDF page to learn more.