Lung interstitial infiltration by chronic lymphocytic leukemia (CLL) is a rare but well known entity, while pleura infiltration by leukemic cells represents a very uncommon manifestation of the disease. Biopsy is the way to establish an accurate diagnosis of lung and pleura infiltration by leukemic cells. A 85-years old female patient, with known B-cell CLL, was admitted to the hospital for recurrent right sided pleural effusion and negative cytologic examination of the exudative fluid. The white cell count on admission was 39x109/L. Lung and pleura biopsy obtained by direct vision thoracoscopy under local anesthesia, which was performed for the determination of the cause of recurrent pleural effusion, confirmed the infiltration of lung and pleura by leukemic B-lymphocytes. Recurrent pleural effusion associated with CLL is a rare event during the course of the disease and thoracoscopy is a useful diagnostic tool. Pneumon 2006,19(2):146-150.