Trajectory calculations suggest that, at energies above twice the critical energy for reaction, molecular rotation and molecular vibration generally make equal contributions to the specific rate constant k(E) for the unimolecular isomerization of CH3NC; an exception is for exceedingly high values of the angular momentum (greater than or equal to 40h). However, for unrandomized molecules, K rotational energy (i.e., propeller motion) is moderately inhibiting, but end-over-end rotation has no effect.