This document discusses HIV and periodontium. It begins with an introduction and overview of the history and epidemiology of AIDS. It then discusses the CDC definition and classification of AIDS, the virus structure, modes of transmission, and life cycle of HIV. It covers the clinical features and WHO classification of HIV-associated diseases. It also discusses the classification of oral lesions associated with HIV, periodontal manifestations, diagnostic tests, and occupational exposure and post-exposure prophylaxis. Management of HIV-infected patients and precautions are outlined.