Ecotoxicology is the science of predicting effects of potentially toxic agents on natural ecosystems and on nontarget species. This course gives students an integrated view of ecotoxicology, from molecules to ecosystems. This course first describes the molecular structures, properties, and environmental fate of pollutants. It then describes the effects of pollutants on living organisms at the molecular, cellular, and individual levels. This course then addresses a question of great interest to ecologists: What effects do pollutants have at the levels of population, community, and the whole ecosystem? Finally, concept of ecological risk assessment will be introduced.