We have described the case of a 73-year-old female patient affected by multicentric Castleman's disease and complicated by Kaposi's sarcoma. Histologically the specimens of nodal biopsy showed combined patterns, both the hyaline-vascular type and the plasma cellular one. We have discussed the relationship between classic Castleman's disease and the multicentric type and the meaning of its association with Kaposi's sarcoma. Both diseases may present in immunologically depressed patients, but it is unknown whether Kaposi's sarcoma is a consequence of immunologic alterations caused by Castleman's disease or whether both processes are due to a primitive disorder of immunologic regulating factors.