The α7β1 integrin was originally identified and isolated from differentiating skeletal muscle and shown to be a laminin-binding protein (Song et al. (1992) J. Cell Biol. 117, 643-657). Expression of the α7 gene and protein are developmentally regulated during skeletal muscle differentiation and have been used to identify cells at distinct stages of the myogenic lineage (George-Weinstein et al. (1993) Dev. Biol. 156, 209-229). The lactoside-binding protein L14 exists as a dimer and has been localized on a variety of cells, in association with extracellular matrix. During myogenesis in vitro, L-14 is synthesized within replicating myoblasts but it is not secreted until these cells commence terminal differentiation and fusion into multinucleate fibers (Cooper and Barondes, J. Cell Biol. (1990) 110, 16811691). Addition of purified L-14 to myogenic cells plated on laminin inhibits myoblast spreading and fusion, suggesting that the L-14 lectin regulates muscle cell interactions with the extracellular matrix that are germane to myogenic development (Cooper et al. (1991) J. Cell Biol. 115, 14371448). We demonstrate here, using affinity chromatography and immunoblots, that α7β1 also binds to fibronectin and to the L-14 lectin. L-14 binds to both laminin and to the α7β1 integrin, and it can effectively inhibit the association of laminin and this integrin. Modulation of α7β1 interaction with its ligands by L-14 is selective: L-14 does not bind to fibronectin, nor does it interfere with the binding of fibronectin to α7β1. These results are discussed in the context of the potential roles of α7β1 in its interaction with laminin and fibronectin during myogenesis.