Castleman disease, an unusual condition of unknown cause consisting of a massive proliferation of lymphoid tissue, remains a clinicopathologic diagnosis. Three histologic variants (hyaline vascular, plasma-cell, and mixed) and two clinical types (localized and multicentric) of Castleman disease have been described. To analyze the clinical features, management, and outcome of patients with Castleman disease. Case series. University referral hospitals. All patients with Castleman disease who were seen at Texas Medical Center, Houston, Texas, between 1977 and 1995. Surgical excision for localized disease; surgery, combination chemotherapy, or prednisone for multicentric disease. Patients were identified according to initial presentation as having localized or multicentric Castleman disease. Patients within each group were further subdivided according to whether they had hyaline vascular, plasma-cell, or mixed disease. Data from 15 patients were analyzed. All 7 patients with localized disease underwent surgical excision and remain free of disease. The 8 patients with multicentric disease were further subdivided according to initial treatment: Three patients who received combination chemotherapy are currently alive and free of disease; 2 patients treated with prednisone are alive but have needed intermittent maintenance therapy for disease reactivations; and 2 patients treated with surgery only have died, 1 of infectious complications and 1 of non-Hodgkin lymphoma. Localized and multicentric Castleman disease are different clinical disorders with overlapping histologic features. Localized disease can be cured with surgery, but complete remissions in patients with multicentric disease have been achieved only with chemotherapy or prednisone given at the time of diagnosis.