Low grade CLL/SLL can evolve to a spectrum of various morphologic higher grade malignancies showing Reed-Sternberg like cells. The evolution towards Hodgkin's disease is rare but frequently associated with the presence of scattered RSL cells within the small lymphocyte proliferation of the CLL/SLL. The evolution towards a Richter's syndrome is more frequent and it can exhibit CD30 positive Reed-Sternberg like cells. In these Richter's syndrome cases, regarding the morphology and the phenotype, it seems likely that there is a spectrum of lesions between true HD and large cell NHL. In the present study, the authors report two cases of transformation of CLL/SLL in non immuno-suppressed patients; one evolved to a morphological and immunohistochemical Hodgkin's disease and the second to a NHL (Richter's syndrome) with numerous Reed-Sternberg like cells. In both cases, EBV has been detected within RSL cells by immunohistochemistry and in-situ hybridization (ISH). So, the role of EBV is suggested in that kind of transformation.