Despite considerable research effort, the molecular mechanisms that underpin sperm-oocyte interactions remain to be fully resolved.  Such information is key to resolving the aetiology of human infertility and for informing the development of new and effective contraceptive agents that can exclusively target gametes and inhibit the fertilisation cascade.  One approach that holds considerable promise for simultaneously addressing both of these issues is the use of phage display technology.  Phage display is an in vitro screening technique that enables selection of binding partners for myriad target types by iterative rounds of affinity partitioning (biopanning).  In studies conducted to date, we have used the technique of phage display to analyse the surface architecture of denuded mouse oocytes and acrosome-reacted spermatozoa with a view to identifying peptides capable of binding with high affinity and specificity to these cells. This approach has been successful in isolating a number of peptides with a high degree of sequence homology with dominant proteins implicated in sperm-egg interactions, in addition to a number of potentially novel ligand-receptor relationships.  Importantly, through the use of competitive sperm-egg interaction assays, we have also been able to demonstrate a significant reduction in both sperm-egg binding and fusion following pre-incubation of eggs in bacteriophage capable of binding to the surface of the gamete. Preliminary data secured using synthetic peptides representing the peptide inserts in the corresponding phage clones have revealed identical patterns of gamete localisation and bioactivity. Such findings have provided the stimulus for a number of exciting avenues of future research including the coupling of the peptides to cytotoxic agents with a view to increasing their contraceptive efficacy. Ultimately this work promises to aid in the elucidation of molecular mechanisms that underpin mammalian fertilisation and the development of novel contraceptives.