The primary and secondary toxicity of warfarin, sodium monofluoroacetate (Compound 1080), and methyl parathion were assessed in the mink, a representative surrogate mammalian wildlife carnivore. In a 28-day test, a LC50 value for mink fed warfarinper se (primary toxicity) was calculated to be 11.7 ppm (mg/kg) with a 95% confidence interval of 9.2 to 15.0 ppm (mg/kg) and a slope of 2.03. Feeding mink warfarin-contaminated rabbit (minus digestive tract contents) incorporated into diets to provide warfarin residue levels equivalent to the warfarin concentrations fed in the LC50 primary toxicity test did not produce secondary toxicity, suggesting that warfarin may be readily bound and/or metabolized into non-, or less-toxic metabolites by a primary consumer. Toxic residues of sodium monofluoroacetate for mink (as in secondary toxicity) were not produced in rabbits fed a lethal dose of this compound when the gastrointestinal tract contents were removed from the rabbit carcasses. These results suggested that reports of secondary toxicity from sodium monofluoroacetate may be primarily due to consumption of the unmetabolized compound from the gut of prey species. Attempts to produce primary and secondary toxicity in mink by feeding methyl parathionper se (primary toxicity) or via contaminated rabbit (containing the gastrointestinal tract contents), as in secondary toxicity, were unsuccessful, as the mink rejected the methyl parathion-treated diets.