The majority of extramedullary plasmacytomas involve the upper respiratory tract but only a few are associated with serum monoclonal gammopathy. Most extramedullary plasmacytomas respond to local radiotherapy and have a better prognosis than multiple myeloma. Solitary plasmacytomas, involving the pleura, are very rare. This case report describes a patient with a solitary extramedullary plasmacytoma involving the pleura, and no evidence of serum, urine or pleural fluid paraproteins. Diagnosis was made by strongly positive immunohistochemical stains with CD38, CD138 and MUM-1 of the pleural tumour. The response to both radiotherapy and chemotherapy was poor and the patient died shortly after diagnosis.