Collagen type IV, laminin, heparan sulfate proteoglycans, nidogen (entactin) and BM‐40 (osteonectin, SPARC) represent major structural proteins of basement membranes. They are well‐characterized in their domain structures, amino acid sequences and potentials for molecular interactions. Such interactions include self‐assembly processes and heterotypic binding between individual constituents, as well as binding of calcium (laminin. BM‐40) and are likely to be used for basement membrane assembly. Laminin, collagen IV and nidogen also possess several cell‐binding sites which interact with distinct cellular receptors. Some evidence exists that those interactions are involved in the control of cell behaviour. These observations have provided a more defined understanding of basement membrane function and the definition of new research goals in the future.