Exciplex laser photolysis at 248 and 308 nm wavelengths coupled with gas-chromatographic analysis was applied to determine the photodissociation quantum yield of acetone (QY). At 308 nm, QY has been found to decrease with decreasing temperature (T = 323-233 K) and to decrease with increasing pressure (P = 13-998 mbar synthetic air) supporting the recent suggestion that the photolysis of acetone plays a less important role in the chemistry of the upper troposphere than previously thought. Water vapour has no effect on QY in disagreement with a recent publication. (c) 2007 Elsevier B.V. All rights reserved.