Clostridia are rare causes of pleuropulmonary infections in the absence of penetrating chest injuries; only 10 previous cases have been reported from civilian practice. An additional case of a rapidly progressive, necrotizing pneumonia and empyema is reported. Clostridial pneumonia is more likely to occur in patients with underlying pleuropulmonary disease. Unlike clostridial myonecrosis, it is rarely associated with toxemia; its mortality rate is comparable to that of nonclostridial pleuropulmonary infections. Appropriate antimicrobial therapy with surgical drainage of the empyema is the treatment of choice. Among the cases reviewed, an iatrogenic cause of infection involving an invasive procedure into the pleural cavity could be identified in seven of 11 cases. Aspiration of oropharyngeal contents was the likely route of infection in three other cases. In the remaining case, bacteremic seeding of the pleural cavity was the most probable mode of infection.