Prostacyclin derivatives of general Formula I ##STR1## wherein R.sub.1 is the residue OR.sub.3 wherein R.sub.3 means hydrogen or alkyl of 1-10 carbon atoms substituted, if desired, by halogen, aryl, C.sub.1 -C.sub.4 -alkoxy, or C.sub.1 -C.sub.4 -dialkylamino; cycloalkyl, aryl, or a heterocyclic residue; or is the residue NHR.sub.4 wherein R.sub.4 means hydrogen, an alkanoyl residue, or an alkanesulfonyl residue of respectively 1-10 carbon atoms,A is a --CH.sub.2 --CH.sub.2 -- or trans--CH.dbd.CH--group,W is a ##STR2## wherein the OH-group can be respectively esterified with a benzoyl or alkanoic acid residue of 1-4 carbon atoms, or can be etherified with a tetrahydropyranyl, tetrahydrofuranyl, C.sub.1 -C.sub.4 -alkoxyalkyl, or tri(C.sub.1 -C.sub.4 -alkyl)-silyl residue, wherein the free or esterified OH-group can be in the .alpha.- or .beta.-position,D and E jointly mean a direct bond orD is a straight-chain or branched alkylene group of 1-5 carbon atoms,E is an oxygen atom or a direct bond,R.sub.2 is a straight-chain or branched-chain alkyl group of 1-6 carbon atoms, a straight-chain or branched-chain alkenyl group of 2-6 carbon atoms which can be substituted by phenyl, halogen, or C.sub.1 -C.sub.4 -alkyl and, if D and E jointly represent a direct bond, is an alkynyl residue of 2-6 carbon atoms optionally substituted in the 1-position by halogen or C.sub.1 -C.sub.4 -alkyl,R.sub.5 is a hydroxy group which can be esterified with an alkanoic acid residue of 1-4 carbon atoms or which can be etherified with a tetrahydropyranyl, tetrahydrofuranyl, alkoxyalkyl, or trialkylsilyl residue and, if R.sub.3 is hydrogen, the salts thereof with physiologically compatible bases, and a process for the preparation thereof.The compounds exhibit blood-pressure-lowering and thrombocyte-aggregation-inhibiting activity.