The present review is restricted to the collation and evaluation of information describing the excretion profile and ecotoxicity of veterinary medicines developed specifically for the control of either internal or external parasites of livestock. It identifies numerous gaps in our knowledge and highlights our poor understanding of the environmental fate of many of these chemicals, especially those developed for the control of ticks, lice, and/or biting flies. Residues of most anthelmintics are largely harmless to dung-feeding arthropods, but those of many ectoparasiticides, especially the synthetic pyrethroids, are highly toxic to fly larvae and adult dung beetles. Organophosphates, because they are metabolized extensively and eliminated mostly in urine, are considered to be unlikely to have a major impact on the development or survival of dung-dwelling organisms. The present review stresses the need for better information regarding spatial and temporal usage patterns of veterinary parasiticides, and it examines the role of ecotoxicological models for evaluating their impact on populations of dung-dependent arthropods.