Nearly all hematologic malignancies can occasionally present with or develop pleural effusions during the clinical course of disease. Among the most common disorders are Hodgkin and non-Hodgkin lymphomas, with a frequency of 20 to 30%, especially if mediastinal involvement is present. Acute and chronic leukemias, myelodysplastic syndromes, are rarely accompanied by pleural involvement. Furthermore, 10 to 30% of patients receiving bone marrow transplantation develop pleural effusions. In cases of hematologic pleural effusions, drug toxicity, underlying infectious, secondary malignant or rarely autoimmune causes should be carefully sought. In most cases, the pleural fluid responds to treatment of the primary disease, whereas resistant or relapsing cases may necessitate pleurodesis.