Patients developing Hodgkin's disease (HD) after a diagnosis of chronic lymphocytic leukemia (CLL), are frequently included in a series of patients with Richter's syndrome (RS). We sought to determine the natural history of the association of CLL and HD. Over a 21 year period, 1374 patients with CLL have been registered in our computer data base. Seven cases of CLL and HD have been documented and confirmed. The median age of these patients was 71 years (range 44-77) and clinical features included male gender (86%), B symptomatology (86%), rapidly progressive lymphadenopathy (71%), prior CLL therapy (71%), advanced Ann Arbor stage (86%), marrow involvement with HD (43%), and autoimmune hemolytic anemia (29%). HD was documented by excisional lymph node biopsy in six cases and splenectomy in one. Mixed cellularity HD was shown in six and nodular sclerosis in one. Five of the biopsies revealed intervening areas consistent with small lymphocytic lymphoma. The Sternberg-Reed (SR) cells were CD15+ in 6/7 cases, and Ki-1+ in the 6 patients tested. CD45 and CD20 staining of the SR cells was nonreactive. The median time to development of HD was 45 months (range 0 to 96). The overall responses to different chemotherapy regimens was approximately 25% with only one CR. Six patients have died at 3, 9, 10, 13, 15 and 36 months and one patient is alive with progressive disease at 11 months. Our data suggests that CLL patients have a heightened risk for HD, features of advanced HD on presentation, and a poor response rate with short survival.