Syntheses of several stable PGI2 analogssubstituted by halogen atoms(s) at C-5 or(and) C-7 are described. Reaction of protected PGI2 methyl ester () with -chlorosuccinimide gave 5-chloro-Δ6-PGI1 derivative (), which was transformed into 5-chloro- and 5,7-dichloro-PGI2 [() and ()] by subsequent isomerization or chlorination. Similarly, reaction of with -bromosuccinimide gave 5-bromo-Δ6-PGI1 derivative