Threshold photoelectron-photoion coincidence spectra of CH3CN were measured in a region 15.1-16.5 eV. We observed a small vibrational enhancement on dissociation of CH3CN+ and obtained kinetic energy releases for channels C2HN+ + H-2 and CH2+ + HCN. The kinetic energies released in channel C2HN+ + H-2 are substantial; a linearly extrapolated dissociation threshold of 14.68 +/- 0.01 eV agrees with a Gaussian-3 B3LYP prediction 14.70 eV for formation of HCCN+ + H-2. In contrast, the small releases for channel CH2+ + HCN agree with a statistical calculation. We describe a plausible dissociation mechanism with the Gaussian-3 B3LYP method to rationalize experimental results. (c) 2007 Elsevier B.V. All rights reserved.