A 52-year-old man with multiple myeloma developed cutaneous nodules while being treated with melphalan and prednisolone. A biopsy specimen showed dermal infiltration by well differentiated plasma cells similar to those found on bone marrow biopsy. The use of peroxidase anti-peroxidase to demonstrate the monoclonality or polyclonality of the cytomplasmic immunoglohulins in the tumor cells revealed a positivity for IgG and 1 chain (ie, monotypic staining). Ultrastructurally, each plasmacytoma cell contained varyting amounts of rough endoplasmic reticulum and Golgi-apparatus. The cutnneous nodules completely disappeared after radiotherapy