We hereby report the occurrence of a non-secreting multiple myeloma (MM) during the course of chronic lymphocytic leukemia (CLL). A 73-year-old patient developed a non-secreting MM 7 years after the diagnosis of CD5 (+) B cell CLL. He received intermittent chlorambucil and prednisolone therapy. The occurrence of tumors in the frontal bone led to resection of the tissue and histopathologic examination revealed neoplastic plasma cell islands within the CLL infiltration. There was no immunoglobulin or light chain accumulation in the serum. Clonal relationship between these diseases has been shown by comparing the isotypes and idiotype of both the heavy and light chains. In our case, the MM was of non-secreting type and thus we could not establish any relation between the 2 disorders. Such a case has not been reported until now in the literature. CLL and MM in the same patient is a rare occurence and investigation of the transformation event at the molecular level will contribute to our understanding of B-cell ontogenesis.