Laminin is a major basement membrane protein and comprises three subunits: α, β, and γ chains. Among these chains, only laminin α chain is capable of signaling via receptors. Endocrine cells of anterior pituitary gland respond to basement membrane proteins, and there is two-layer of basement membrane, endothelial cell side and parenchymal cell side, in the gland. However, there is no information about the component of two-layer of basement membrane in the gland. In this study, we used immunohistological techniques to observe five laminin α chains (α1-α5) in rat anterior pituitary gland. Laminin α1, α3, α4 andα5 chains immunoreactivities were noted in the basement membrane of the gland. In addition, laminin α1, α3 andα5 chains were located in the basement membrane on the parenchymal cell side of the gland. The basement membrane on the endothelial cell side contained laminin α4 and α5. These findings show that two-layer of basement membrane is constituted of different components in the gland. Difference in composition implies that two-layer of basement membrane has different function in the gland.