The histopathology of severe lupus glomerulonephritis comprises distinct patterns of injury which were initially defined by the World Health Organization Classification of 1982 as focal and segmental glomerulonephritis (category III), diffuse proliferative glomerulonephritis (category IV) and complex membranous glomerulonephritis (categories Vc, Vd). It is assumed that the morphologic abnormalities demonstrated in this classification represent distinctive differences in the mediation of the immune response which leads to a specific type of glomerular inflammation. In 1995 the World Health Organizational committee recommended a change in categorization of focal and segmental glomerulonephritis (class III) and diffuse proliferative glomerulonephritis (class IV), which would overlook the morphological differences between these categories and treat them as a continuum, recommending that biopsies classified as focal and segmental glomerulonephritis (category III) with involvement of > or =50% of glomeruli be included into the diffuse proliferative glomerulonephritis category (category IV). Since the classification of severe lupus nephritis has significant impact on prognosis and the therapeutic approach to patients with this disease, it is the purpose of this review to critically re-examine the existing classification based on new insights into differences in morphologic features and long-term outcome.