Parasitized steers were used to contaminate 3 pastures containing dung beetle populations of different densities. Six parasite-free calves were then allowed to graze the pastures for 43 to 45 days. Two calves that grazed a pasture with dung beetle population rendered lower than normal by screening and trapping acquired 9 times more parasites than 2 calves that grazed a pasture which captured beetles were released. Two calves that grazed a pasture with a natural dung beetle population acquired 4 times more worms than the calves on pasture with the increased beetle population. The results indicated that the 2 major genera of nematodes present (Ostertagia and Cooperia) were significantly reduced in number by dung beetle activity.