Chicken Infectious Anemia (CIA) is caused by a circovirus with a worldwide distribution. The disease, that is clinically manifested as bone marrow atrophy, anemia and severe immunosuppression affects mostly 2-4-week-old chickens, that are infected via the «vertical» route. Characteristic PM findings include atrophic thymus, spleen and bursa of Fabricius. Mortality reaches 20% and surviving birds show retarded growth. Secondary infections (due to immunosuppression) are common sequelae of CIA outbreaks. Live vaccines are used to prevent CIA breeder-progeny transmission.