S U M M A R Y Multiple laminin isoforms including laminins 5 (a3 b3 g2), 6 (a3 b1 g1), 10 (a5 b1 g1), and possibly laminins 7 (a3 b2 g1) and 11 (a5 b2 g1) are present in the epidermal basement membrane. However, only the precise epidermal ultrastructural localization of laminin 5 (a3 b3 g2) has been elucidated. We therefore determined the precise expression and ultrastructural localization of the a5, b1, b2, and g1 chains in the epidermis. The expression of laminin chains in skin samples was analyzed from patients with epidermolysis bullosa (EB, n515) that harbor defects in specific hemidesmosome (HD)-associated components. The expression of the a5, b1, and g1 chains (present in laminins 10/11) and b2 chain (laminins 7/11) was unaffected in all intact (unseparated) skin of EB patients including Herlitz junctional EB with laminin-5 defects (n56). In the basement membrane of human epidermis, the a5, b1, b2, and g1 chains were expressed but also localized to the dermal vessels. Immunogold electron microscopy of normal human epidermis localized the a5, b1, b2, and g1 chains to the upper lamina densa, with between 84%