The infrared multiphoton dissociation (IRMPD) of acetic acid was studied by photofragment translational spectroscopy. Carbon dioxide and methane were observed for the first time as products from dissociation under collisionless conditions. The product translational energy distribution for this channel peaks well away from zero, which supports a four-center transition state. A previously observed channel, resulting in the formation of ketene and water, was verified. The average translational energy release for the former channel was measured to be 26.4 kcal/mol, and a value of 18.6 +/- 2 kcal/mol was obtained for the dehydration channel. With a laser fluence of 12 J/cm(2), decarboxylation accounts for roughly 35% of the total dissociation yield.