Anthelmintic resistance is a major problem in sheep husbandry all over the world. One way toslow down the development of anthelmintic resistance is to keep part of the parasitepopulation in Refugia (unexposed to drugs) which will maintain the genes for susceptibilitywithin the population. Climate, type of parasite and drenching regimes effect the size of theRefugia. Dilution of resistant with susceptible parasites, targeted treatment and targetedselective treatment are all management strategies that employ Refugia. Dilution is possible butcomplicated.