After oxidative sulfitolysis of normal rabbit IgG, two fractions (LI and LII) of light chains were separated by gel filtration on Sephadex G 100 in acid-urea. More than half of the light chains in the LI fraction (b-n) lacked antigenic determinants associated with the b locus (b+) and shared antigenic determinants with a distinct type of light chain (b-s) previously isolated from the sera of rabbits suppressed for genetic expression of b locus allotypes. The LII fraction, representing about 80% of the total light chain population from normal b5 rabbits, was found to be largely if not entirely composed of b+ light chains. Both b-n and b-s light chains were found to be antigenically distinct from b+ light chains. This supports the hypothesis that rabbit b- light chains obtained from normal or suppressed rabbits correspond to λ type chains.