In this series of 72 cases of empyema, 28 patients (38.8) had anaerobes isolated from their pleural fluid cultures. In 22 patients, anaerobes were the only isolates, and in six there were also aerobes. This observed frequency (38.8%) of anaerobic empyema is notably greater than the frequency noted in an earlier study (1952 to 1967) from the Veterans Administration Medical Center, Wood, Wis, while the contribution of various pathogenetic mechanisms was similar. Although closed chest tube drainage was instituted initially in 51 patients, 18 patients (35%) subsequently required additional procedures. The case-fatality ratio was 51.4% in this study compared with 46.6% in the earlier study. Twenty-two patients died during the same hospitalization period while the empyema was an active problem. Six (8.3%) of these empyema-related deaths occurred in patients without underlying disease, while 16 (22.2%) were in patients with underlying diseases.