Basement membranes (BMs) are thin layers of extracellular matrix (ECM) found at the basal surface of many cell types, including epithelial cells. BMs present growth, differentiation, and anti-apoptotic signals and provide structural support to cells, compartmentalize tissues, and serve as filters. The structure and function of BMs depend on their complement of laminins, a family of alpha beta gamma heterotrimeric glycoproteins. We found that laminins containing the alpha2 and alpha4 chains are the major laminins in pancreatic acinar BMs. Importantly, these laminins were required for proper basal localization on acinar cells of two laminin receptors, dystroglycan and integrin alpha6beta4 .