Combinatorial antibody libraries, in which PCR amplified immunoglobulin light and heavy chain DNA are randomly recombined irrespective of their pairing in vivo into a vector and subsequently expressed in E. coli, have quickly become a very productive tool to generate monoclonal antibodies from various species. It has been drastically improved by utilizing phage display technologies in the selection process of specific antibodies. A brief summary of current techniques, critical published experiments showing the versatility of these systems with emphasis on human antibodies and discussions on chain preference, affinity maturation and the advent of semisynthetic and non-immune libraries will be presented.