Primary cutaneous plasmacytomas are very rare. In this report, we describe two such cases and review the literature on this entity. Both patients presented with a slowly growing, painless, and solitary mass on the chest wall. Histologically, one case was composed of mature-looking plasma cells, while the other was composed of immature and anaplastic plasma cells, infiltrating the dermis. The epidermis was spared. Kappa light-chain restriction was demonstrated by immunohistochemical techniques in both cases. There was no evidence of marrow disease even on repeated marrow biopsies, although extracutaneous lesions were detected in one patient. One remained in complete remission 6 years following local irradiation. The other patient was treated with local irradiation and systemic chemotherapy, with a complete response, but this was followed by multiple cutaneous recurrences and further remissions by treatment with cytotoxic agents. The present cases and those reported in the literature illustrate well the variable clinical course of primary cutaneous plasmacytoma. Although cure can apparently be achieved in some patients by local radiation therapy, more than half of the cases relapse or progress to myelomatosis. The disease-related mortality is at least 40%. Thus cutaneous plasmacytoma appears to be more aggressive than noncutaneous extramedullary plasmacytomas and should be separately categorized from them in future studies.