Staphylokinase, a profibrinolytic bacterial protein, was cloned into Escherichia coli, following the amplification of its gene via PCR. The amplificated gene was inserted in a pKK223-3 plasmid vector. The recombinant protein (STAR), expressed from a tac promoter, was obtained in the periplasmic space when IPTG was added to the culture medium. Both the concentration of the inducer as well as the growth phase of recombinant cells at which it was added affected the final yield of periplasmic STAR. The protein was purified by a one-step procedure in an acylated-plasminogen Sepharose coupled column.