Abstract: 13-Thiaprostanoic acid derivatives of the formula ##STR1## wherein A is --CO-- or --CHOH--, B is --CH.sub.2 --CH.sub.2 -- or --CH=CH--, R.sup.1 is H or alkyl of 1 to 4 carbon atoms, m is a whole number from 0 to 5, n is a whole number from 0 to 3 or, when B is --CH=CH--, additionally 4, 5, 6, 7, 8 or 9, R.sup.2 is alkoxy of 1 to 4 carbon atoms, phenoxy, pyridyl, thienyl, naphthyl, phenyl substituted by F, Cl, Br, OH, OCH.sub.3 or OF.sub.3 or phenoxy substituted by F, Cl, Br, OH, OCH.sub.3, CH.sub.3 or CF.sub.3 or, when B is --CH=CH--, additionally hydrogen, phenyl or tolyl, R.sup.3 is H, methyl or ethyl, possess pharmacological activity, including blood pressure lowering activity.