This chapter discusses human immunodeficiency virus (HIV) and head and neck cancers, where HIV is a blood-borne retrovirus that induces clinical disease by causing progressive depletion of CD4+ T lymphocytes, which are the key cells in the cell-mediated immune system that protects the human system from viral, fungal and protozoal infections and neoplastic growths. Severe immune suppression can predispose the individual to develop the opportunistic infections and malignancies of acquired immune deficiency syndrome (AIDS). Persons infected with HIV have an increased risk of several cancers involving the head and neck region and are considered AIDS-defining, such as of Kaposi sarcoma (KS) and non-Hodgkin lymphoma (NHL). KS is a mesenchymal tumor involving blood and lymphatic vessels, where KS usually manifests as multiple purple-red vascular nodules and plaques of the skin and mucosa or viscera.