The reaction of dihaloethylenes with acetate anions in the presence of palladium (II) salts gave trans-diacetoxyethylenes catalytically. It was found that the system, PdCl 2–NaOAc– CH 3 CN is the best for the diacetoxylation of dihaloethylenes, and that palladium (II) salts catalyze the isomerization of trans-diacetoxyethylene to its 1, 1-diacetoxy derivative. The mechanism was also discussed.