1. Introduction Phage display technology was first introduced by George P. Smith, who integrated protein coding fragments into filamentous bacteriophage M13 and the process of selection of desired protein fragment was named as panning [1].  Phage display is an inexpensive technology exploited for exogenous peptides, aiding increased target affinity and interaction [2]. It integrates the principles of genetic engineering with combinatorial chemistry. In general, phage display is composed of a system where exogenous DNA is interested in a filamentous phage genome along with the phage coat encoding sequence. Expression leads to the phage particles that express the sequence of interest in fusion with on the coat protein. These sequences are capable of interacting with various external targets/ligands. One of the significant characteristics of phage display is the production of large number of libraries and hence, these libraries can be used for the determination of the functional peptides with desired properties [3]. Proteins, peptides and antigens depend on the conformational changes to attain complete structural and functional characteristics. Immunization methods are barrier to this whereas, phage display method can be used to determine peptides and antigens for several ranges of epitopes and peptides [1]. M13 bacteriophage is the most commonly used phages for the purpose, owing to its flexible cylindrical protein structure and a large number of coat proteins including pIII, pVI, pVIII,pVII and pIX. pIII coat protein is responsible for the attachment of the bacteriophage virus to the pilus of the bacteria. After the attachment of pIII to the membrane protein, the genome of the phage is transferred into the bacteria where it is converted into a double stranded DNA and synthesis of new proteins occur around single stranded phage genome. The final phage particles are extruded from the bacteria, however, M13 phages do not kill the bacteria and remain in the constant phase of infection and growth [4]. The basic process of phage display is summarized in figure 1.        1.1 Natural and synthetic peptide library: In term of peptides, phage libraries are either composed of natural peptides or synthetic ones. Natural peptide libraries are constructed by extracting DNA fragments from the organism (example: mice) and inserting it into the phage particle. As a result, phage particles, on their surface, express natural peptides. However, synthetic libraries are composed of cloned synthetic and randomly generated oligomeric sequences inserted into the phage genome [4]. 1.2 Antibodies-based libraries Several small antibody fragments such as; scFv (variable light and heavy chain fragments joined by polypeptide linker), Fab (antigen binding region) have been used to prepare phage libraries. These antibody-based libraries are widely used for epitope mapping, by biopanning of the antigen or the whole cell [5]. These libraries can naive that is, they are generated by extracting antibodies antigen-immunized animals. Whereas, nonimmunized libraries are constructed by rearrangement of antibody fragment, extracted from the healthy B cells. The process is achieved by the means soeing PCR (polymerase chain reaction) [4].    1.3 BiopanningFollowing the amplification and infection of the bacteriophage viruses in the bacteria, the obtained phages are used for the biopanning process. The process involves introduction of the libraries to the target (cell, antigen, receptor or other proteins) bound onto the solid surface. Unbound phages are washed and removed whereas, bound ones are eluted, and the results are analyzed by the means ELISA (enzyme linked immunosorbent assay). In order to obtained high affinity and specific phages, 4-5 rounds of panning are performed using the phages obtained from the preceding rounds [6].This review is designed to highlight some of the significant applications of phage display in the field of medical sciences, implemented as a tool for diagnostic and therapeutic medicine.