The kinetics of the order–disorder transition in solid carbon monoxide by a tunneling mechanism are considered. The rate of the transition is found to be much smaller than the rate of barrier penetration. An estimate of the rate is made using the best current estimate of the twofold barrier to end-for-end rotation in solid carbon monoxide; it appears that the rate of ordering will be unobservably slow. The rate is very sensitive to the barrier height and might become observable if the barrier were smaller by a factor of 2. The energy levels of the two-dimensional double-minimum hindered rotor have been calculated as a function of barrier height and are tabulated.