RESUMO
Three examples of spontaneous malignant lymphoma were observed in owl monkeys 23, 81, and 183 days after arrival in our laboratories. The pathological features of the disease were analogous to experimentally induced Herpesvirus saimiri lymphoma. H. saimiri was recovered from 2 animals (it was not attempted from one case) and one isolate was shown to reproduce characteristic H. saimiri malignant lymphoma. Each monkey originated in Peru in contrast to our usual source of owl monkeys which originate in Barranquilla, Colombia. Samples collected from owl monkeys in Peru did not reveal antibodies to H. saimiri nor were virus isolated from cocultured leukocytes. Squirrel monkeys in the same geographical location all carried H. saimiri. The observations indicate that H. saimiri lymphoma can occur as a spontaneous disease and that the virus can cross the same taxonomic lines in nature as in the laboratory.