Acetonitrile, an atmospheric trace gas of very low concentration, is believed to be primarily removed from the stratosphere by reaction with hydroxyl radicals. Another possible way for destruction of atmospheric acetonitrile, attack by chlorine atoms, {A figure is presented} was investigated in this work. The corresponding rate constant was measured at 370 and 413 K using a competitive method. It was established that this reaction, with an activation energy of 6 kcal mol-1 and a pre-exponential factor of 5 × 1010 mol-1 s-1 (or 8 × 10-11 cm3 s-1), is several orders of magnitude slower under atmospheric conditions than the reaction of acetonitrile with hydroxyl radicals.