Fifteen patients (11 males, four females; median age 57) manifested a disease characterized by (1) the histopathologic features of Castleman's disease, plasma cell type, in lymph node biopsies; (2) predominantly lymphadenopathic disease, involving multiple, preferentially peripheral nodal groups; (3) varied manifestations of multisystemic involvement (such as constitutional symptoms; splenomegaly and hypergammaglobulinemia; elevated ESR, anemia, and thrombocytopenia; hepatomegaly and altered liver function tests (LFTs); signs of renal disease); and (4) idiopathic nature. Two main patterns of evolution were recognized: persistent, with sustained clinical manifestations, and episodic, with recurrent exacerbations and remissions. Seventy-three percent of patients had infectious complications, and 27% developed malignancies. Complete remissions were obtained occasionally with antineoplastic agents and with splenectomy but not with glucocorticosteroids alone. The median survival time is 30 months; 60% of patients have died. Median follow-up in the six surviving patients is 97 ± months. A review of 50 cases in the literature revealed similar clinical and laboratory features. Despite some similarities with autoimmune diseases, the main features of this process seem to best fit a hyperplastic-dysplastic lymphoid disorder in a setting of immunoregulatory deficit.