We investigated the ability of the meadow vole, Microtus pennsylvanicus, to produce tannin-binding salivary proteins when fed quebracho tannin-containing diets or when injected with the drug isoproterenol. None of the treatments induced production of new salivary proteins. None of the salivary proteins from voles bound tannin in vitro, and none of the proteins in vole saliva reacted with antibodies to tannin-binding proteins from saliva of rats. Diets containing 2.9% crude quebracho tannin had no effect on growth or survival of voles. Voles consuming diets containing 6% crude quebracho tannin had increased rates of loss of body mass and mortality and decreased rates of food consumption early in the trial, but began to accommodate to the diet by the end of the 10-day trial. Voles fed diets containing 6% tannin prepared by moistening and heating a mixture of lab chow and quebracho tannin had significantly higher rates of mortality than voles fed 6% tannin added directly to dry chow. Nitrogen, dry matter, and caloric digestibilities did not differ significantly among treatments.