We have analyzed by the limiting dilution assay on spleen cells from (NZB x NZW)F1 hybrid mice the repertoire of lipopolysaccharide-responsive murine kappa- and lambda 1-secreting B cells committed to the production of anti-DNA autoantibodies to determine the contribution of the heavy and light chains to anti-DNA specificities. Our results demonstrated that anti-DNA precursors were predominantly found in the kappa-secreting B cell population, but not in lambda 1-secreting B cells, while anti-hapten, dinitrophenyl, and anti-tetanus toxoid activities were distributed fairly well in both populations of B cells. This suggests that the V kappa gene segments are critically involved in the generation of anti-DNA specificities, and that at least at the germ-line gene level, the heavy chain V region genes by themselves are not able to confer the anti-DNA autoreactivity.