We undertook a retrospective review of five patients with pseudo-chylothorax diagnosed at our hospital between 1984 and 1994. Pseudo-chylothorax was diagnosed if crystals of cholesterol were observed (CC) or if cholesterol concentrations were over 150 mg/dl, but chylomicrons were absent from pleural effusions with cloudy supernatants after centrifugation. The five patients were males and their mean age was 53 years. All had history of pulmonary or pleural tuberculosis (mean 31 years since diagnosis). All had received chemotherapy and four had undergone therapeutic pneumothorax. Two patients were diagnosed in the course of examination for other reasons, Three were diagnosed while being examined for the cause of pleural effusion. The diagnosis of four patients was based on the presence of CC. Three patients received specific treatment and Mycobacterium tuberculosis was isolated in the pleural fluid of two. One patient required a pleural drain and antibiotics because of empyema related to pseudo-chylothorax. Decortication was needed by two. 1) Pseudo-chylothorax is at present rare. 2) All the cases we saw were associated with earlier tuberculosis infection with residual pleural lesions. 3) Diagnosis usually occurs in the course of examination for the other motives, but the possibility of infected pleural effusion or reactivation of tuberculosis should be considered.