Autoreactive B-cells constitute a substantial part of B-cell repertoire. They frequently secrete polyspecific natural autoantibodies which are the expression of germinal genes. During recent years, considerable evidence has accumulated indicating that autoreactive B-cells frequently undergo malignant transformation. This evidence arose from the study of monoclonal immunoglobulins (MIgs) and from recent studies of chronic lymphocytic leukemia (CLL) and non Hodgkin lymphoma (NHL) B lymphocytes. The present review, includes two sections. The first one reviews evidence supporting the idea that autoreactive B-cells constitute a substantial part of autoreactive B-cell repertoire. The second one is devoted to review evidence favouring the view that this autoreactive B-cell repertoire is frequently involved in B-cell malignancies.