The absence of laminin alpha 2 chain causes muscle cell degeneration and peripheral dysmyelination in congenital muscular dystrophy patients and dy mice, suggesting its role in the maintenance of sarcolemmal architecture and peripheral myelinogenesis. Here we demonstrate the secretion of laminin alpha 2 chain in cerebrospinal fluid (CSF). Laminin alpha 2 chain was detected as a minor component of the total CSF proteins or glycoproteins. Laminin alpha 2 chain was localized in the cytoplasm of epithelial cells of choroid plexus, suggesting active secretion. Our results suggest that immunochemical analysis of CSF laminin alpha 2 chain could be useful as an aid for the diagnosis of congenital muscular dystrophy.