Overtone‐induced isomerization of methyl isocyanide to methyl cyanide is studied by using classical trajectories on several potential‐energy surfaces. The several potential‐energy surfaces are variations of a potential which we have developed based on available experimental and ab initio results. The trajectory results for simple potentials which neglect stretch–bend interactions show that overtone excitation of a CH stretch to the v=6 level at total energies (including overtone excitation energy) of 75, 125, and 150 kcal/mol does not enhance the rate of isomerization. However, at an initial total energy of 200 kcal/mol, the isomerization rate is enhanced by as much as a factor of 3 by selective excitation of a CH stretching overtone. However, the mode specificity is sensitive to the potential‐energy surface. When a more realistic potential is used in which the bending force constants are attenuated as a function of the bond lengths or in which nondiagonal quadratic coupling terms are included, the domina...