Recent advances have been made in the development of systems for the display and expression of recombinant antibodies and affibodies in filamentous phages, Escherichia coli and other prokaryotic cells. Emphasis has been placed on improving phage and phagemid vectors, alternative systems for expression in different cellular compartments (e.g. the outer membrane, periplasm, cytoplasm and extracellular secretion) and novel multimerization systems for generating bivalent or multivalent binding molecules.