A 56-year-old man was admitted to our hospital because of bilateral pleural effusion. Computed tomography revealed solitary mediastinal lymphadenopathy, splenomegaly and a small amount of ascites. No lung parenchymal lesion was seen. Although lymphocyte predominance without atypia and a high adenocine deaminase concentration in the pleural fluid were compatible with tuberculous pleurisy, no mycobacteria could be detected either with Ziehl-Nielsen stain or with PCR. Because the serum soluble interleukin 2 receptor (sIL-2 R) level was unexpectedly high (> 8,000 U/ml), and a level not previously reported in benign diseases, we performed thoracoscopy- and mediastinoscopy-assisted biopsies, both of which eventually confirmed the diagnosis of tuberculosis. After a 4-drug anti-tuberculous regimen was initiated, pleural effusion and ascites subsided, with a marked decrease in the sIL-2R level. This case indicates that in tuberculous pleurisy, serum sIL-2R can rise to a level suggestive of hematological malignancies, it and also illustrates the validity of thoracoscopy-assisted pleural biopsy in such situations.