This issue of Veterinary Clinics: Food Animal Practice, guest edited by Dr. Ray M. Kaplan, focuses on Ruminant Parasitology. This is one of three issues each year selected by the series consulting editor, Dr. Robert A. Smith. Articles in this issue include, but are not limited to: biology and epidemiology of GI nematode parasites in cattle, epidemiology and control of GI parasites of cattle in southern climates, epidemiology and control of GI parasites of cattle in northern climates, anthelmintic resistance and strategies for sustainable control of parasites, refugia-based strategies for parasite control in livestock, epidemiology and control of liver flukes, diagnostic methods in livestock parasitology, parasite vaccines, what Modeling parasites, transmission and resistance can teach us, fecal egg count reduction tests in cattle and small ruminants, ectoparasites of ruminants, ruminant coccidiosis, neosporosis, toxoplasmosis, and sacocystosis in ruminants, girdiasis and cryptosporidiois in ruminants, biology, epidemiology and control of GI nematodes in small ruminants, and realistic approaches to parasite control in ruminant livestock.