Publisher Summary Choice of an appropriate route of administration for chemical agents is a crucially important aspect of the experimental design of fish exposures. This chapter discusses several approaches for administering chemical agents to fish and describes their potential research applications. Numerous methods exist for exposing fish to waterborne chemicals. Exposure chambers can be simple containers such as beakers or fish tanks, using solvent-rinsed glass containers for organic chemical exposures and acid-washed (2% nitric acid) plastic containers for metal exposures. Many types of in-situ cages are available for fish exposure to contaminants in the natural environment. For adult or juvenile fish, cages are usually constructed of aquaculture mesh stretched over a cylindrical or rectangular frame fabricated from metal or PVC pipe. Dietary administration is often the method chosen for administration of therapeutic agents in aquaculture. Fish can also be exposed to many types of chemical agents through consumption of contaminated prey. This method works best with contaminants that are easily bioaccumulated by the prey species, including many hydrophobic organic compounds and heavy metals. The most common method of administering a bolus dose to fish is by injection. Ideally the chemical agent is dissolved directly in physiological saline. However, hydrophobic chemicals may be dissolved in very small quantities of a co-solvent prior to dilution with saline.