This issue of Veterinary Clinics of North America: Small Animal Practice focuses on Immunology and Vaccination, with topics including: Recent Advances In Vaccine Technologies; Immune System's Response to Vaccination; Current Vaccine Strategies for Dogs and Cats; Update on Therapeutic Vaccines; Common and Newly Recognized Autoimmune Diseases; Adverse Response to Vaccination; Vaccines in Shelters and Group Settings; Evidence vs Belief in Vaccine Recommendations; Effects of Aging on the Immune Response; and Use of Antibody Titer to Determine the Need for Vaccination.