Abstract Herpesviruses were isolated from lymphocytes from four of eighteen spider monkeys imported recently from Colombia, South America. Virus was isolated after circulating lymphocytes were co‐cultivated with permissive cell cultures. Three isolates induced fatal malignant lymphomas in cotton‐topped and white‐lipped marmoset monkeys and one isolate which was also tested in squirrel monkeys caused no overt disease in this animal species. These virus isolates shared cross‐reacting antigens with Herpesvirus saimiri but possessed distinguishing biological properties.
