Background: KSHV, Kaposi’s sarcoma-associated herpesvirus, is a necessary cofactor for the development of Kaposi’s sarcoma (KS). We have previously reported KSHV-related DNA sequences in retroperitoneal fibromatosis (RF) tissue from two species of macaque. The putative herpesvirus was called RFHV for RF-associated herpesvirus. These data suggested that KSHV is a human representative of a larger family of primate herpesviruses. Objective: To identify and characterize other members of a putative family of KSHV-related herpesviruses in macaques in order to obtain information on the evolutionary history of KSHV infection in humans. Study design: Lymphoid tissue cells and blood leukocytes from rhesus-, cynomolgus- and pigtailed-macaques were tested for the presence of unknown herpesviruses using degenerate primer-driven PCR amplification. The sequences obtained were compared against known herpesvirus sequences. Results: We have identified new herpesvirus DNA sequences in each of the three macaque species. Sequence comparisons indicate that these new viruses are most related to each other and form a separate phylogenetic lineage within the γ herpesviruses. Screening of PBMC from Indonesian-origin quarantine animals suggests that these viruses (MGV, macaque γ virus) are species-specific, and highly prevalent in the wild. They are readily cultured in vivo, and share a common tissue tropism with the previously identified RFHV. Conclusions: MGV and RFHV represent two independent introductions of an ancestral γ herpesvirus into macaque precursors.