The authors report two cases of myelomatosis localised to the pleura, one of which was associated with an adenocarcinoma. Pleural effusions are relatively rare during the course of multiple myeloma and most often occur with non-specific disorders of the disease. The myelomatous origin of a pleural effusion can only be made by analysis of the pleural fluid and should be recognised early enough to enable aggressive treatment to be instituted even if the prognosis associated with such a localisation is very poor.