Eighty patients required surgical drainage of infections in the pleural space or lung during a four-year period (1984-1987). Thirty-nine patients had a history of heavy intravenous drug use and 28 of those not addicted to drugs were addicted to alcohol. Impaired immunity was believed to be present in 72 (90%) due to malnutrition (45 patients), acquired immunodeficiency syndrome (AIDS) or AIDS-related complex (13), hepatic cirrhosis (1), diabetes (1), or multiple causes (12). Sixty-four patients had acute purulent empyema; 9, tuberculous empyema (often a mixed infection); 2, tuberculous pleural effusion with complications; 2, lung abscesses requiring open drainage; 2, chronic bronchopleural fistulae; and 1, empyema secondary to an esophageal perforation. Fifty-three (66%) were treated with tube thoracostomy only and 27 required additional procedures, including open drainage (19 patients), decortication (5), lung resection (2), chest wall resection (1), and parietal pericardiectomy (1). Overall mortality was high (30%); mortality had a strong correlation with malnutrition or immune deficiency. Very low serum albumin levels were common and were the most important single determinant of a fatal outcome: (table; see text) Other important determinants of mortality were: total lymphocytes less than 1000 (50% mortality); anergy to tests for delayed hypersensitivity (39% mortality); AIDS or AIDS-related complex (54% mortality). Analysis of the records of the 24 patients who died has led to the conclusion that despite the advanced disease present and the poor condition of most patients at least one third of the deaths could have been avoided if important errors in diagnosis and medical or surgical management could have been prevented.(ABSTRACT TRUNCATED AT 250 WORDS)