A review. The use of .beta.-strand mimetics has expanded in recent years to include compds. developed for protein-protein interactions involving many types of protease enzymes, kinases (including allosteric or type 3 kinase inhibitors), and SH2 and PDZ domains; and for interacting with .beta.-sheet structures including disruption of amyloid formation. The availability of new drug-like scaffolds that can be used to preorganize mols. in .beta.-strand shapes, either alone or in combination, looks to be a promising strategy for developing enzyme inhibitors, receptor antagonists, and perhaps strand-constrained vaccines. Since we now know of receptor classes that specifically recognize the peptide .beta.-strand, this strategy may be successful for receptor classes even when the specific receptor structure is unknown. Strand mimetics also raise the possibility, because of their rigidity, of potential uses in protein surface mimetics as part of longer scaffolds designed to sep. attached protein/peptide motifs over long distances, thereby mimicking discontinuous protein surfaces. Strand mimetics might also be incorporated into polypeptides to investigate effects of templating in protein folding. Directed strategies toward the development of nonpeptidic analogs of the peptide .beta.-strand, in combination with serendipitous discovery of .beta.-strand mimetics, should expand significantly in the coming years. We encourage further studies to create new designed .beta.-strand mimetics and to identify the importance of the .beta.-strand structure in other examples of protein recognition.