Castleman's disease represents an atypical lymphoproliferative disorder, infrequently associated with various immunologic abnormalities or subsequent development of malignancy such as Kaposi sarcoma, malignant lymphoma and plasmacytoma. Its clinicopathologic features depend on various etiologic factors such as Kaposi sarcoma herpesvirus (KSHV), oversecretion of IL-6, adhesion molecule and follicular dendritic cell dysplasia, etc. To investigate the relationship of Castleman's disease (CD) and the above factors, we reviewed 22 cases of CD. Four cases of KSHV positive CD were detected, all multicentric, plasma cell type, and these cases displayed prominent vascular proliferation, characteristic 'Kaposi-like lesion'. IL-6 and CD54 positive mononuclear cells were scattered in interfollicular areas of KSHV positive cases. Follicular dendritic cell hyperplasia, vascular proliferation, expression of IL-6 and CD54 did not show any significant difference between solitary vs multicentric type, and plasma cell type vs hyaline vascular type. Our study suggests that KSHV positive CD reveals unique pathologic features, and the probable relationship of KSHV and IL-6 and CD54 is discussed.