The search for a transmissible infectious agent as the cause of Kaposi's sarcoma lead to the discovery in 1994 of Kaposi's sarcoma-associated herpesvirus (KSHV), also known as human herpesvirus type 8 (HHV8). KSHV is the only human gamma2 herpesvirus (rhadinovirus) known so far, and is also associated with two other AIDS-related lymphoproliferative disorders: primary effusion lymphoma (PEL) and the plasma-cell variant of multicentric Castleman's disease (MCD). This review addresses key aspects of KSHV epidemiology, life cycle and pathogenesis, including the role played by key latent and lytic KSHV genes.