Multiple myeloma affects predominantly osseous spaces and the close vicinity of bones. A plasmacellular exudate is rare. The authors describe the course of plasmacellular leukaemia in a 68-year-old female patient where the first symptom of the disease was anaemia and a dextrolateral pleural exudate with a cytological finding of plasma cells. The exudate disappeared after the first cycle of chemotherapy and intrapleural administration of cytostatic. After the third cycle of chemotherapy remission of the disease was recorded which was, however, short. After three months' remission (six months after establishment of the diagnosis) the disease exacerbated violently, the dextrolateral exudate reappeared and gradually the insufficiency of the infiltrated bone marrow increased. The patient died one month after the relapse of the disease. The finding of a plasmacellular exudate must be considered the sign of a very poor prognosis and in that case very aggressive treatment is indicated.