Abstract In this letter the kinetics of the reaction of hydroxyacetone CH3C(O)CH2OH with Cl atoms is investigated using the relative rate technique. Experiments are carried out in a 65L multipass photoreactor in the temperature range of 281–350K. A mid-infrared spectrometer based on a quantum cascade laser in external cavity emitting at 9.5μm is used to analyze the reactants. The determined rate coefficient for the investigated reaction is (1.7±0.3)×10−11exp(381.5±57.3/T). The results are presented and discussed in terms of precision and compared with those obtained previously. The impact of Cl atoms on the atmospheric life time of hydroxyacetone is also discussed.