The human antibody response to the capsular polysaccharide of Haemophilus influenzae type b (Hib) is a good model for examining human V region repertoires. While the VLrepertoire of human antibodies to Hib polysaccharide is relatively simple and dominated by the product of a germline VkII gene named A2, at least five other VLgenes can be expressed by some individuals. These include at least two VkI products and at least one VkIII, one VkIV, and one V?product. The epitope recognized by a monoclonal anti-idiotype antibody is on the A2 VkII product. © 1992 The University of Chicago.