Pleural involvement in brucellosis is very rare. Current knowledge on brucella pleuritis is limited to a few case studies, and pleural adenosine deaminase (ADA) in brucellosis has not been studied previously. We report the pleural fluid characteristics, including ADA, of two cases with brucella pleurisy. Analysis of the pleural fluids revealed exudative effusions with increased ADA level, decreased glucose concentration, and lymphocyte predominance. The similarity with tuberculous pleurisy was remarkable. We suggest that brucellosis should be considered in the differential diagnosis of tuberculosis, especially in regions endemic for both diseases. Copyright (C) 2002 S. Karger AG, Basel.