The etiology of a disease in rhesus monkeys the main clinical manifestation of which was acute conjunctivitis of an epizootic character has been studied. The cytopathogenic agent well propagating in primarily trypsinized kidney cells of monkeys has been isolated when investigating the affected eye mucosa. It was not pathogenic for laboratory animals. The mean diameter of the virions is 75 nm, the buoyant density in CsCl is 1.34 g/cm3, the viral DNA density is 1.706 g/cm3. The biological properties and findings of physicochemical, electron-microscopic, and serologic investigations allow one to allocate the isolated agent to the SV-37 strain, a representative of the adenovirus group.