The relationship between the clinical parameters and chest film appearance was studied in patients with active pulmonary tuberculosis. Patients with extended disease were often malnourished and had weak tuberculin reaction accompanied by lymphopenia. They excreted a large amount of mycobacterial bacilli and a longer period was required for negative conversion of sputum culture. We confirmed that the criteria for chest roentgenogram classification established by the Japanese Society for Tuberculosis ("Gakkai Classification") is useful in the estimation of the risk of infection and the prognosis of tuberculosis patients.