We describe a 40-year-old white man with a peculiar skin eruption in association with polyclonal hypergammaglobulinemia. No underlying disease was detected. A skin biopsy specimen showed a proliferation of mature plasma cells intermingled with some lymphocytes and histiocytes, an appearance consistent with cutaneous plasmacytosis. This disease had been previously described only in Japanese patients. In our patient the disease progressed slowly. Lymph node infiltration by mature plasma cells was later noted.