Palladium acetate has been shown to be a highly active catalyst for Heck reactions of aryl chlorides even in the absence of organic ligands. Bromobenzene can efficiently be coupled in presence of negligible traces of Pd, resulting in the highest TON (4.7 x 10(7)) and TOF (1.2 x 10(7) h(-1)) values that have ever been reported for this system up to now.