Human monoclonal antibodies (MAbs) are more suitable than MAbs of animal origin for clinical applications because of lower hypersensitivity reactions, less formation of circulating immune complexes, and lower anti-immunoglobulin responses. The classical production of human monoclonal antibodies via the hybridoma technique or Epstein-Barr virus (EBV) transformation is limited by the instability of cell lines, low antibody production, and the problems of immunizing humans with certain antigens (1,2). A promising alternative is the production of human recombinant antibodies (3). Recombinant DNA technology has made it possible to clone human antibody genes in vectors and to generate antibody expression libraries (4–7). One approach has been to amplify and recombine the IgG repertoire of an “immunized” donor. This has been used to isolate several antibodies that were related to diseases (8–10). In order to obtain more universal antibody libraries the naive IgM and the IgG repertoire of several “unimmunized” donors were pooled (11–14). The complexity of the combinatorial libraries has been further increased by creating so called “semisynthetic” or “synthetic” antibody libraries (15–20).