The lock‐in threshold of a single‐mode 0.633‐&mgr; He&sngbnd;Ne laser was measured. Experiments were performed with a 1:1 mixture of the20Ne and22Ne isotope. The lock‐in threshold was found to increase with operation of the laser with smaller excess unsaturated gain. Minimum lock‐in threshold was found to occur at a higher frequency than the frequency at which the output power was a maximum. A rotational mode competition between the oppositely directed traveling waves was found for rotation rates less than the lock‐in threshold. The beam traveling with and against the direction of rotation was found to decrease and increase, respectively, with increasing rotation rate. Analysis showed that the single‐mode‐ring, laser equations, with mode coupling due to backscattering, satisfactorily explained the experiments.