Aim of the present study is to examine the morphological aspects of monoclonal gammopathies (GM) detectable by bone marrow biopsy. With reference to Multiple Myeloma (MM), the more important disease of this group from a clinical standpoint, other conditions will be later evaluated. Particular attention will be given to Monoclonal Gammopathy of Undetermined Significance (MGUS) that still today is characterized by wide shadows concerning both ethiology and evolution significance.