Phage display is a molecular technique by which foreign proteins are expressed at the surface of phage particles. Such phage thereby become vehicles for expression that not only carry within them the nucleotide sequence encoding expressed proteins, but also have the capacity to replicate. Using phage display vast numbers of variant nucleotide sequences may be converted into populations of variant peptides and proteins which may be screened for desired properties. It is now some seventeen years since the first demonstration of the feasibility of this technology and the intervening years have seen an explosion in its applications. This review discusses the major uses of phage display including its use for elucidating protein interactions, molecular evolution and for the production of recombinant antibodies.