Ring neutrophils in plasma cell dyscrasia. Sporadic reports in the medical literature concern the significant incidence of neutrophils with ring-shaped nuclei in myeloproliferative disorders. We report our first encounter with ring neutrophils in patients with lymphoproliferative disorders. A significant incidence of ring neutrophils was observed in all of 20 patients with multiple myeloma and in nine of 10 patients with monoclonal gammopathy of undetermined significance. The mean percent of ring neutrophils was 9.5% (range, 1.0% to 28.0%) in patients with multiple myeloma, which was significantly greater than in those with monoclonal gammopathy of undetermined significance or in healthy controls. In multiple myeloma, the incidence of ring neutrophils in the pretreatment phase was greater than that in the remission phase. A great deal of overlap was noted between multiple myeloma in the remission phase and monoclonal gammopathy of undetermined significance. The incidence of ring neutrophils seemed to vary according to disease stage. Ring neutrophils may reflect abnormal granulopoiesis in plasma cell dyscrasias. 