The incidence of empyema has been drastically reduced with the advent of antimicrobial drugs,however,there is still complicated and difficult problems of management of empyema remaining. During the period of December, 1958 to December, 1962, 90 patients nf empyema thoracis were managed in the Department of Thoracic Surgery of the National Medical Center, and this series deals with the incidence,etiologic consideration, bacteriology and management of empyema with its result. 1] Male predominates with the ratio of 3.1: 1, and peak age incidence lies in 3rd decade. 2] Most common etiologic factor is bronchorespiratory infection among which tuberculosis remains highest incidence. 3] 56.7% of patients shows positive result of bacteriologic study and about half of positive culture series shows mixed infection or changing pattern of bacteriological strains during serial examinations. 4] Complete cure is obtained in 84.4% of patients with 5 deaths.