This article describes two patients with localized Castleman's disease (CD) of the mixed hyaline vascular and plasma cell type located at the mesentery of the small bowel, associated with systemic symptoms, anemia, an increased plasma level of acute phase reactants, and systemic amyloidosis. There were amyloid deposits on the vascular walls of the liver, spleen, and mesenteric lymphoid mass. On immunohistochemical studies, amyloid was shown to be of the AA type in both cases. After surgical resection of the mesenteric mass, clinical and laboratory manifestations improved, and the amyloidosis showed no progression in these patients 23 years and 1 year later. The authors' review of the literature shows a striking similarity of CD cases associated with amyloidosis in terms of the abdominal localization of the lymphoid mass, secondary pattern (AA type) of amyloidosis, and improvement of clinical manifestations after removal of the tumor, without progression of amyloid deposition.