We have isolated overlapping cDNA clones encoding the entire kalinin B1 chain. The predicted sequences are consistent with the models proposed for the structure of this chain as a truncated homologue of the B1 chain of laminin. The percent sequence homology with other laminin B1 chains is relatively low, suggesting that this chain is functionally different. The sequence of the VI domain of this chain is consistent with the possibility that it serves to bind specifically the kalinin A chain and subsequently covalently binds to it. In keeping with the accepted nomenclature for the laminin chains we name this novel polypeptide the laminin B1k chain.