Epizootic streptococal infction is one of the common disease in guinea pig. We have confirmed 54 case of epizootic streptococal infection in guinea pig by histopathology and epidemiology. Grossly infection is characterized by the presense one to several enlarged lymph nodes particularly of the mandible cervical lymph nodes and accompanied by pleuropneumonia. Histologically there were lymphadenitis with abscesses surrounded by loose connective tissue fibrinopurulent pneumonia pleuritis myocarditis pericarditis and peritonitis. Epidemiological survey revealed that mortality was high in young adult female(15.1%) and changeable weather season such as spring and fall. From findings it was suggested that epizootic streptococal infection of guinea pig begin to infect in breeding colony around weaning period and died from that infection at animal facility during the quarantine period.