The development of glomerulonephritis in NZB/W mice is closely related to the formation of antinuclear, particularly anti-DNA, antibodies. The developing inflammatory glomerular lesions are characterized by the deposition of γG- and β1C-globulins plus DNA and possibly other nuclear antigens, presumably as complexes, in a granular to lumpy pattern along the capillary walls and in the mesangia. Elution studies revealed the γG-globulin in the glomeruli to be largely γG2A-type antibody to soluble nuclear antigens. Enhancement of the antinuclear antibody response by active immunization of young NZB/W mice with DNA-methylated BSA hastens the development and increases the severity of the glomerulonephritis. Similarly, injections of soluble DNA into NZB/W mice with circulating anti-DNA antibodies but with as yet little nephritis causes rapid progression of nephritis