Streptavidin-binding peptides containing the consensus amino acid sequence motif EPDW were identified using a phage display library. Phage presenting peptides containing these sequences bound streptavidin in a biotin-sensitive fashion and could be eluted with biotin. The previously identified 'streptag' peptide sequence (AWRHPQGG) competed with phage presenting the EPDW consensus sequence for streptavidin binding. Furthermore, the EPDW sequence has two amino acids in common with yet another previously identified streptavidin-binding sequence, GDWVFI, which has similar biochemical properties. Binding inhibition studies revealed that residues flanking EPDW, as well as residues of the modified phage pIII product to which displayed peptides are fused, contributed to streptavidin binding. The derivation of small molecules based on the structure of peptides selected using display methods is a potentially important application of phage display technology. The relevance of the observations made here for that application are discussed. Finally, a group of 'nuisance' peptides of the consensus sequence WHWWXW, whose binding specificity has not been fully elucidated, but which have been isolated in a number of biopanning experiments, including those that do not utilize streptavidin, are also described.