Pleural biopsies are especially indicated in the following circumstances: a) inconclusive pleural fluid analysis and negative sputum study, if adenosine deaminase (ADA) levels are unavailable; b) suspected multi-resistant tuberculosis; c) a need for differentiating tuberculous pleurisy (if it progresses with neutrophilia) and complicated parapneumonic effusion; d) malignant pleural effusion coexisting with very high ADA levels; e) effusion coexisting with lung cancer and negative pleural cytology; f) suspected mesothelioma; and g) need for implementing re-treatment for patients with relapse after chemotherapy.