Because of the dispute in the literature over the dissociation rate and energy partitioning of the acetone molecule upon photoexcitation to the S-1 state (pi*<--n) and 3s Rydberg state (3s<--n), we have remeasured the lifetime of acetone (also d(6)-acetone) on the S-1 and 3s surfaces by a femtosecond time-resolved multiphoton ionization technique, coupled with a reflectron time-of-flight mass spectrometer. The measured dissociation rate of acetone on the S-1 surface is prompt, and the acetyl radical is long lived. The lifetime of acetone on the 3s surface is measured to be 3.2 +/- 0.4 ps (6.0 +/- 0.5 ps for d(6)-acetone). The dissociation rate of acetyl is approximately 1.7 ps (2.5 ps for d(3)-acetyl) from the curve fitting. This agrees well with the Rice-Ramsperger-Kassel-Marcus theory predicted lifetime of 1.0 ps (1.9 ps for d(3)-acetyl) when the internal excitation energy of the acetyl radical is treated by a statistical-adiabatic-impulsive model.