Herpesvirus ateles is an agent indigenous to spider monkeys (Ateles spp.) and causes fulminant lymphomas in various New World primates. Structural and genetic relatedness led to the classification of this virus as a member of the genus Rhadinovirus. It is most closely related to Herpesvirus saimiri. The 108,409-bp light DNA segment of the herpesvirus ateles strain 73 genome has two genes for U-RNA-like transcripts and 73 open reading frames, of which at least 6 show significant homologies to cellular genes (encoding complement control proteins, apoptosis-regulatory proteins, D-type cyclins, interleukin-8 receptors, and enzymes involved in nucleotide metabolism). The left terminal region of the light DNA segment bears the putative rhadinovirus oncogene tio.