Abstract: New inter-m-phenylene-PGI.sub.2 derivatives are prepared of the general formula I ##STR1## wherein R.sup.1 stands for hydrogen, alkyl containing 1 to 4 carbon atoms or a pharmaceutically acceptable primary, secondary, tertiary or quaternary ammonium cation or a metal cation,R.sup.2 and R.sup.3 stand independently on each other for hydrogen, alkanoly, aroyl or an acetal type or alkyl silyl type protecting group,R.sup.4 represents hydrogen or an alkyl group containing 1 to 4 carbon atoms,X stands for oxygen, or a--CH.sub.2 --group,Y stands for--C.tbd.C-- or a trans--CH.dbd.CW group, wherein W stands for chlorine, bromine or fluorine,Z represents an alkyl group having 6 to 9 carbon atoms, optionally substituted by one or more alkyl groups containing 1 to 4 carbon atoms or fluorine or it stands for an optionally substituted arylmethyl or aryloxy methyl group.The new compounds are active ingredients of pharmaceutical compositions having antiaggregatory activity.