Primary Sjogren's syndrome (pSS) is a chronic autoimmune disease with well-documented association of lymphoid malignancies during the progress of the disease. Although several types of malignancy and pseudomalignancy have been reported in pSS, low-grade non-Hodgkin's lymphomas are the most frequently observed. Reactive plasmacytosis mimicking myeloma is a very rare condition in association with pSS. We describe a 72-yr-old woman with pSS who presented with hypergammaglobulinemia, and extensive bone marrow and lymph node plasmacytosis, which mimicked multiple myeloma. In this patient, there was an abnormal differentiation of memory B cells to plasma cells in the peripheral blood suggesting underlying pathogenetic mechanism for this condition.