Vibrio parahaemolyticus is a halophilic Gramnegative facultative anaerobe commonly found in estuarine waters and in seafood like shellfish. It has been implicated in outbreaks of gastro-enteritis in several countries [1]. Food borne illness caused by V. parahaemolyticus results chiefly from the consumption of insufficiently heated or raw seafood, especially in the summer months. The standard method for detection of V. parahaemolyticus (Bacteriological Analytical Manual procedure) is a culture-based procedure which can take up to four days for positive identification. Recent outbreaks of V. parahaemolyticus related illnesses have heightened the need to develop a rapid and reliable method to detect this pathogen in shellfish. PCR methods, based on the amplification of the toxin producing genes, unfortunately give false postive results with other Vibrio species [2]. In our studies we have used phage antibody display to differentiate between pathogenic V. parahaemolyticus and other pathogenic and non-pathogenic Vibrio sp.