Recent developments in the application of eukaryotic recombinant protein techniques have provided new tools with which to dissect and map functional activities in basement membrane glycoproteins. This has been particularly valuable in the case of laminins where the relationship between structure and function has been difficult to establish. Several characteristics of the laminins lie at the heart of the problem. First, the molecules are very large, each assembled from three multidomain subunits joined in a long-coiled coil Fig. 1). Second, laminins bear substantial disulfide and carbohydrate modifications that are crucial for proper conformation. Many, perhaps most, laminin activities present in native laminin are lost upon heat- or chaotropic-denaturation. Native activities are often not retained in short peptides or even in recombinant fragments generated in prokaryotic cells. Furthermore, there is evidence to suggest that synthetic laminin peptides can exhibit “cryptic” activities not found in native protein.