5-cis-15(R)-Iloprost is the C-5 cis-isomer and 15(R)-epimer of iloprost, a second generation structural analog of PGI2 (prostacyclin). Iloprost displays ten-fold greater potency than the first generation stable prostacyclin analogs, typified by carbaprostacyclin. There are no published studies of the pharmacological properties of 5-cis-15(R)-iloprost.