A 39-year-old woman complained of anterior chest pain. A lateral chest X-ray film showed destruction of bone in the body of sternum. CT scan showed a soft tissue density within the sternum. Serum protein electropheresis revealed mild monoclonal gammopathy of IgG-kappa, but the urine contained no Bence-Jones protein. A biopsy specimen showed plasmacytoma with cytoplasmic Ig IgG-kappa. Bone scintigraphy and systemic bone roentgenography revealed only the lesion in the sternum. Sternal subtotal resectin was performed. The defect of the anterior chest wall was reconstructed with double folded marlex mesh and pedicles from the major pectoral muscle. Iliac bone marrow aspiration revealed no evidence of myeloma. There was no serum evidence of monoclonal gammopathy two months after the operation. Therefore, the final diagnosis was solitary plasmacytoma of the sternum. It is now 41 months since surgery, and there have been no signs of fecurrence. Long term follow up is necessary in this case.