The authors present an overview of the presence of residues from veterinary medicinal products, growth-promoting agents and performance enhancers in food-producing animals, as a result of administering these substances--legally or illegally--on farms. The current situation in the European Union (EU) is represented by an analysis of the 2004 results from the national residue monitoring plans of EU Member States. Aspects of ante-mortem and postmortem inspection are also considered, as well as the practical challenges facing veterinary inspectors attempting to uncover illegal uses and prevent public health risks. Substances which are considered illegal because their risks have not yet been assessed, such as those employed in minority species or for minor uses, are also discussed.