To characterize a protein's function, it is often advantageous to identify other proteins with which it interacts. The yeast two-hybrid system is one of the most versatile methods available for detection and characterization of protein-protein interactions, and in the recent years it has become a mature and robust technology. A further improvement to this technique is the ability to examine and distinguish more than one interaction simultaneously. This is achieved in the Dual Bait, which has successfully been used to detect proteins and peptides that target specific motifs in larger proteins, to facilitate rapid identification of specific interactors from a pool of putative interacting proteins obtained in a library screen, and to score specific drug-mediated disruption of protein-protein interaction.