Integrin interactions with extracellular matrix proteins are mediated by brief oligopeptide recognition sequences, and synthetic peptides containing such sequences can inhibit integrin binding to the matrix. The RGD peptide motif is recognized by many integrins including ␣v6, a specific receptor for fibronectin thought to support epithelial cell proliferation during wound healing and carcinoma progression. We report here the discovery of an unexpected non-RGD recognition motif for integrin ␣v6. We compared the recognition profiles of recombinant ␣v6 and ␣v3 integrins by using phage display screening employing 7-mer and 12-mer peptide libraries. As predicted, phages binding strongly to ␣v3 contained ubiquitous RGD sequences. However, on ␣v6, in addition to RGD-containing phages, one-quarter of the population from the 12-mer library contained the distinctive consensus motif DLXXL. A synthetic DLXXL peptide, RTDLDSLRTYTL, selected from the phage sequences (clone-1) was a selective inhibitor of RGD-dependent ligand binding to ␣v6 in isolated receptor assays (IC 50 ؍ 20 nM), and in cell adhesion assays (IC 50 ؍ 50 M). DLXXL peptides were highly specific inhibitors of ␣v6-fibronectin interaction as synthetic scrambled or reversed DLXXL peptides were inactive. NH 2 -and COOH-terminal modifications of the flanking amino acids suggested that the preceding two and a single trailing amino acid were also involved in interaction with ␣v6. The DLXXL sequence is present in several matrix components and in the  chain of many integrins. Although there is as yet no precise biological role known for DLXXL, it is clearly a specific inhibitory sequence for integrin ␣v6 which has been unrecognized previously.Integrins are a family of heterodimeric class I transmembrane receptors involved in numerous cell-matrix and cell-cell adhesion phenomena (1). They can be grouped roughly into three classes: the 1 series, which are ubiquitous receptors for extracellular matrix (2); the 2 series, which are activatable on leukocytes and are triggered during the inflammatory response (3); and the ␣v series, which bind and mediate the cell response to provisional extracellular matrices found during wound repair and other pathological processes (4).The integrins ␣51 (5), ␣IIb3 (6), ␣81 (7), ␣v1 (8), ␣v3(9), and ␣v6 (10) all bind the Arg-Gly-Asp-(RGD) peptide sequence in fibronectin, where it is presented in a constrained loop (11). Soluble RGD-containing peptides can inhibit the interaction of each of these integrins with fibronectin. However, to analyze the function of individual fibronectin receptors in a particular cellular environment it is useful to have more specific inhibitors, and a variety of inhibitory antibodies, modified peptides, and non-peptidic substances has been developed. However, as yet no inhibitor has been discovered specific for ␣v6. ␣v6 is a rare integrin, induced during repair processes in epithelia (10, 12). Its only known specificities are for fibronectin (10), where it can be the dominant receptor me...