Clinical-, serological and pathological examinations were conducted on twenty feedlot cattle with acute pneumonia from the Department ofLima, in order to determine the etiology ofthe disease. Prior to sacrifice ali the animals were monitored for clinical signs and sera samples taken for serological testing. At postmortem, ali affected lungs were examined grossly and pathological samples were taken to identify viral agents by direct immunoflourescence and/or bacteriological isolation, as well as for histopathological studies.