The cDNA which encodes the mouse counterpart of human plasma hyaluronan-binding protein (PHBP) was isolated and characterized. The clone contained an insert of 2153 bp, which contained the 1674-bp open reading frame coding for a polypeptide of 558 amino acid residues. The amino acid sequence of mouse PHBP predicted from the nucleotide sequence of cDNA shows reasonable homology to that of human PHBP. Like human PHBP, the amino acid sequence predicted from the nucleotide sequence of mouse PHBP cDNA exhibited significant homology to that of human hepatocyte growth factor activator (HGFA).