cDNA encoding a human .alpha..sub.2 -plasmin inhibitor precursor protein represented by an amino acid sequence from the -39th Met to the 452nd Lys in FIG. 1 of the accompanying drawings; an amino acid sequence of a human .alpha..sub.2 -plasmin inhibitor precursor represented by an amino acid sequence from the -39th Met to the 452nd Lys in FIG. 1 of the accompanying drawings; and genomic DNA encoding a human .alpha..sub.2 -plasmin inhibitor protein which is composed of exons II, III, IV, V, VI, VII, VIII, IX and X in FIG. 4 of the accompanying drawings, said exons being bonded to one another via introns.