A theory has recently been developed for the generation of turbulence by unstable tides and gravity waves (Lindzen, 1981). Omitted from this theory was consideration of the possibility that turbulence could be generated by gravity waves which were not convectively unstable (i.e., breaking). The possibility of such generation was suggested by a result of McComas and Bretherton (1977) showing that internal gravity waves are indeed unstable to other gravity waves with shorter wavelengths. The present paper estimates the maximum turbulence which might be generated by such a process and shows that even this turbulence would not greatly alter earlier results.