Kaposi sarcoma-associated herpesvirus (KSHV), also known as human herpesvirus 8 (HHV-8), is discovered in 1994 from Kaposi’s sarcoma (KS) lesion of an acquired immunodeficiency syndrome (AIDS) patient. In addition to its association with KS, KSHV has also been implicated as the causative agent of two other AIDS-associated malignancies: primary effusion lymphoma (PEL) and multicentric Castleman’s disease (MCD). KSHV is a complex DNA virus that not only has the ability to promote cellular growth and survival for tumor development, but also can provoke deregulated angiogenesis, inflammation, and modulate the patient’s immune system in favor of tumor growth. As KSHV is a necessary but not sufficient etiological factor for KS, human immunodeficiency virus (HIV) is a very important cofactor. Here we review the basic information about the biology of KSHV, development of pathogenesis and interaction between KSHV and HIV.