Richter's syndrome is the development of an aggressive diffuse lymphoma in chronic lymphatic leukemia (CLL) and is associated with a poor prognosis. A patient with CLL developed Richter's syndrome, which responded to intensive chemotherapy. Spontaneous regression of CLL in blood and marrow was observed at the onset of Richter's syndrome. The patient remained in complete remission from the lymphoma 4 years after the completion of treatment, and there was no evidence of CLL.