The use of combinatorial libraries displayed on the surface of filamentous bacteriophage offers an efficient route to obtain a diverse set of monoclonal antibodies (MAbs) with desired specificity (1,2). However, following selection of such libraries, certain epitope specificities may dominate the cloned Abs because, for example, the epitope is immunodominant or because Abs to that epitope have a selective advantage in the panning process arising from a higher affinity. Although these attributes may be desirable, other selection conditions are required to recover Abs with different characteristics. In this chapter, an epitope-masking strategy is described by which Abs to an extended range of epitopes can be retrieved from phage-display libraries. The strategy uses antigen (Ag)-specific Fabs or single-chain Abs retrieved by an initial selection of the phage libraries to block the corresponding immunodominant epitope. Reselection of the phage library on the masked Ag refocuses the selection against other epitopes on the Ag (see Fig. 1).