Richter's syndrome is termed as the occurrence of a high-grade lymphoma along with a chronic lymphocytic leukaemia. We report a patient diagnosed as having a CLL evolving into an immunoblastic lymphoma. In spite of this morphologic change, the same identical immunophenotype remained in both types of cells assessed, that is, CLL-type lymphocytes and immunoblastic and lymphoplasmocytoid cells. This event appears to favour the common clonal origin of these two entities.