A 56-year-old man with chronic lymphocytic leukemia who developed Richter's syndrome is described. The criteria for diagnosis are given and the histology is discussed. We agree that Richter's syndrome represents a peculiar complication of chronic lymphocytic leukemia and not a separate disease entity. As such, Richter's syndrome must be known and recognized by those evaluating patients with lymphadenopathy whose basic diagnosis may be confused with Hodgkin's disease or "histiocytic" lymphoma.