A case report of multicentric Castleman's disease associated with Kaposi's sarcoma is presented. Histologic examinations of cutaneous lesions and of an axillary lymph node were made. The cutaneous lesions showed Kaposi's sarcoma and a lymph node revealed Castleman's disease and foci of spindle cells characteristic of Kaposi's sarcoma. The association of Castleman's disease and Kaposi's sarcoma appears too frequently to be due to chance alone. We speculate that these two entities may reflect different tissue reactions to the same causative agent.