This document describes procedures used to collect information, tissues, and fluids for documenting the exposure of fish to environmental contaminants. For the procedures described here, fish are captured (preferably by electrofishing) and held alive until processing (generally <1 h). Fish are weighed, measured, and examined for grossly visible external lesions and pathologies. A blood sample is collected by caudal veinipuncture using a needle and syringe. The fish is subdued and it's abdominal cavity opened. The internal organs are dissected from the fish for examination. The sex of the fish is determined by direct observation of its gonads. The liver is weighed (most species) and cut into small cubes and flash-frozen in cryogenic vials, which are stored and shipped in dry ice or liquid nitrogen. Additional liver cubes plus all grossly visible anomalies are preserved for histopathology. The gonads and spleen are weighed, and samples are preserved for histopathology. The kidneys are examined, and histopathology samples collected. A gill sample is also collected and preserved. All remaining tissues are returned to the carcass, which is wrapped in foil, labeled for chemical analysis, and chilled. Individual fish carcasses are composited by station, species, and gender; frozen; and shipped to the analytical laboratory. Procedures are also described for record keeping; processing blood to obtain serum and plasma; flash-freezing samples; cleaning equipment; and preventing the transport of living organisms among waterways. A list of necessary equipment and supplies is also provided.