Antibodies, in particular human antibodies, are a growing class of new agents with potential diagnostic and therapeutic applications. Advanced DNA and protein technologies allow for the generation of recombinant antibodies in vitro from large DNA libraries. Ribosome display is a cell-free protein display technology that selects desirable antibodies through an efficient search for novel diversity from large populations. The ribosome-selected pools can then be screened rapidly to identify individual antibodies possessing the required activity, without involving the need for cloning by Escherichia coli. The combination of ribosome display, selection and cell-free screening provides a rapid discovery tool for the generation, optimization and modification of antibody-combining sites.