The active form of coagulation factor XIII, factor XIIIa, is a transglutaminase that covalently cross-links fibrin molecules by joining gamma-glutamyl and epsilon-lysyl primary amino groups. In this paper we report the design of a yeast expression vector called pPH3 which includes the GAL1-GAL10 promoter, multiple cloning sites, the URA3 selectable marker, the 2 mu sequences and the ampicillin-resistance gene. We have placed full-length factor XIII cDNA into the PstI site of this vector, transformed the yeast cells and expressed human coagulation factor XIII which was found to be enzymatically active based on observations that this recombinant factor XIII: (a) showed immunological identity with placental factor XIII; (b) was demonstrated to have transglutaminase activity, and (c) cross-linked fibrin in a manner identical to human placental factor XIIIa-catalyzed polymerization (gamma-gamma dimerization and alpha polymerization).