Plasmacytomas of the testes are extremely rare tumors, especially when occurring in the absence of a previous or concurrent diagnosis of multiple myeloma. We present a case of solitary testicular plasmacytoma in a 71-year-old man who had no clinical evidence of myeloma. Immunohistochemical stains showed monoclonal cytoplasmic production of IgA-kappa within tumor cells. A summary of the other reported cases of testicular plasmacytoma is presented. Plasmacytoma of the testes, while occasionally manifesting as a solitary, primary lesion, most likely is a precocious, highly unusual manifestation of systemic multiple myeloma.