This text provides a concise and comprehensive introduction to key immunotoxicological issues for all those interested in, but with no prior knowledge of, this area of toxicology. The first section explores the health consequences of immunotoxicity, namely the adverse effects related to chemically-induced immunosuppression and immunostimulation, hypersensitivity reactions and autoimmune diseases, with an overview of major immunotoxicants. The second part describes the latest methods used to detect and evaluate, preclinically and clinically, the unexpected immunotoxic effects of xenobiotics. Trends in implementing strategies and recent changes to the regulatory aspects are also considered. The third section examines possible future developments, including In Vitro methods, biomarkers of immunotixicity and risk assessment.