The photodissociation of gaseous acetyl cyanide has been examined following excitation at 193 nm. CN X(2) Sigma(+) photofragments were probed via laser fluorescence excitation to determine their rotational, vibrational, and translational energy distributions. CN was produced in v" = 0 and 1 with mean rotational energy (13.5 +/- 2) kJ mol(-1), and v" = 2 with mean rotational energy (10 +/- 4) kJ mol(-1). Mean translational energies of the CN fragments were (32 +/- 10) kJ mol(-1). Ab initio electronic structure theory has been used to characterize the heat of formation for acetyl cyanide along with its geometries and vibrational frequencies. The acetyl cyanide heat of formation, Delta H0(f,0), is predicted to be (-0.4 +/- 8) kJ mol(-1) using Gaussian-2 theory (G2). The theoretical results are used to compute bond dissociation energies of acetyl cyanide for further interpretation of the experimental photodissociation data. Evidence is presented that the majority of CN fragments are produced via dissociation of the parent acetyl cyanide to CH3CO + CN, with subsequent decomposition of the acetyl fragment. The alternate possible primary alpha-cleavage pathway to CH3 + OCCN is proposed as a possible source for the OCCN radical.