In this study we analyzed 15 cases of empyema due to Streptococcus milleri group treated between January 2000 and December 2007. The majority (87%) were men, and the mean patient age was 62 years (range 36 to 83). An underlying disease was present in 14 of 15 cases. Six cases were complicated by pneumonia. Polymicrobial infection with S. milleri group was recognized in four patients. Most patients underwent chest tube drainage (87%), and all received antibiotic treatment (100%). The average duration of chest tube drainage was 8.4 days and that of antibiotic treatment was 14.0 days. Six cases (40%) underwent video-assisted thoracoscopic surgery for decortication. The duration of hospitalization was 19.6 days. The clinical effect of treatment was comparatively good (93%), and the prognosis was also good (mortality rate 7%).