Endoparasitic control is currently limited to grazing strategies and/or the administration of anthelmintic drugs. In tropical countries animals are often fed low protein diets and are subject to nematode infections. Dietary protein level may influence the magnitude of clinical symptoms seen in infected animals (Coop & Holmes, 1996). Other evidence suggests that low concentrations of condensed tannins (often found in tropical plants) may also be effective at reducing parasitic burden in ruminants (Niezen et al., 1994). The following experiments were conducted to observe the effect of protein level and dietary Quebracho tannin (QT) in sheep exposed to a trickle infection of the gastrointestinal nematode Trichostrongylus colubriformis for 10 weeks.