This issue of Veterinary Clinics: Food Animal Practice, guest edited by Dr. Christopher Chase in collaboration with Consulting Editor Dr. Robert Smith, focuses on Ruminant Immunology. Article topics include: Herd immunity: an epidemiologist's view; Genetics of immunoresponsive and correlates of immunity; Microbiome and immunity: an evolving field; Vaccine administration dos and don'ts (endotoxin stacking; delayed MLV); Mycoplasma bovis: interations with the immune system and failure to generate an immune response; Nutriceuticals and their effect on immune response; Adjuvants; Immunology of maximizing passive transfer; Mucosal immunity and common mucosal response; Vaccinating in the face of maternal immunity; and Gamma Delta T cells in ruminants: their role, function, and importance.