Empyema thoracis following pneumonia, trauma, and surgical procedures continues to be a source of major morbidity and mortality. We retrospectively reviewed the hospital records of 100 patients treated for empyema thoracis at San Francisco General Hospital during the past 10 years. The causes of empyema in these patients were as follows: pneumonia 44%, trauma 24%, surgical and invasive procedures 15%, lung abscess 11%, and hematogenous spread 6%. Ten patients in this series died of sepsis from necrotizing pneumonia or overwhelming injuries caused by trauma. Streptococcus (31%), Staphylococcus (21%), and Bacteroides (15%) were the organisms most commonly isolated. Bacterial isolates were single in 55%, multiple 42%, and absent in 3%. The type of organism did not correlate with severity of disease or eventual requirement for thoracotomy, pleural débridement, or Eloesser procedure. Successful methods of treatment included aspiration in 9%, tube thoracostomy in 63%, pleural débridement and drainage in 7%, and an Eloesser procedure in 11%. Because our patients were often debilitated from chronic alcoholism, drug addiction, and major trauma, conservative management was initially tried. In most patients empyema resolved with tube thoracostomy. Pleural débridement should be reserved for patients with special problems such as multiple loculation or purulence inaccessible to percutaneous tube placement. the Eloesser procedure is indicated in patients who have an infected residual pleural space that persists despite adequate tube drainage.