Epithelial tissues perform essential barrier and transport functions in almost all major organs, and the inability to properly form or maintain their polarized architecture has been implicated in various diseases, including cancer. In this issue of EMBO reports , the Milan group implicates the Drosophila gene scarface ( scarf ) in the polarized deposition of basement membrane (BM) proteins (Sorrosal et al , 2010), a process which is crucial for maintaining epithelial structure. Mammalian epithelial cells have a polarized structure maintained by intercellular tight junctions, which separate distinct apical and basolateral plasma membrane (PM) domains. Many proteins have been found to be targeted specifically to either the apical or basolateral PM, where they are unable to diffuse across the tight junctional barrier (Fig 1; Tanos & Rodriguez‐Boulan, 2008). Another defining characteristic of epithelia is the existence of a complex network of secreted extracellular matrix proteins—such as laminin, collagens and heparan sulphate proteoglycans (HSPGs)—at the basal surface of epithelial cells, which are collectively known as the BM (Yurchenco et al , 2004). Basolateral‐specific cell‐surface receptors, such as integrins and dystroglycan, transduce signals from the BM and promote the adhesion of epithelial cells to the substratum. The BM is also crucial for specifying positional cues during the establishment and maintenance of epithelial cell polarity and, consequently, the proper formation of epithelial tissues. Figure 1. How could Scarf and Crag regulate the proper localization of basement membrane proteins to the epithelial basal surface? ( A ) By actively sorting BM cargo—such as laminin (Lam)—into vesicles bound for delivery to the basal surface. ( B ) Through the inhibition of the delivery or fusion of BM‐containing vesicles to the apical domain. ( C ) By removing BM from the apical surface through endocytosis and/or proteolysis. BM, basement membrane; Scarf, Scarface. The vesicular trafficking pathways that are required for the transport …