Following European guidelines, this article presents an environmental risk assessment for four ionophores (monensin, salinomycin, narasin and lasalocid) based on predicted environmental exposure from broiler production in two scenarios. In a third scenario, measured occurrence data are used to characterize the potential risk. Findings show that predicted environmental concentrations in all environmental compartments and measured environmental concentrations in sediments are above predicted no-effect concentrations, so ionophores might pose an environmental risk. The toxicological effect data reviewed revealed that very limited data exist and that long-term effect data and chronic effect data are not available.