The kinetic theory of the modified two-stream instability (MTSI) is usually considered more accurate than the corresponding fluid theory, for the purpose of interpreting VHF and UHF coherent radar backscatter measurements. However, recent developments in the nonlinear theory of the MTSI have retained the fluid theory formalism and consequently may not be entirely valid in the short-wavelength regime where VHF and UHF radars operate. In this paper, a nonlinear kinetic theory dispersion relation which takes account of the nonlinear resonance broadening effects is developed. With the aid of this dispersion relation, the phase speeds of the short wavelength plasma waves are calculated, as functions of wavelength, aspect angle, and flow angle. The results indicate that phase speeds tend to increase with increasing drift speed, at all wavelengths. Furthermore, under given flow conditions, the phase speeds are relatively insensitive to the flow angle and aspect angle but vary considerably with altitude. However, unlike long-wavelength fluid type waves, short-wavelength MTSI waves are moderately dispersive, the shorter wavelengths having the larger phase speeds. Finally, these kinetic theory calculations are also used to estimate the form of the k spectrum of saturated MTSI waves, and the results are compared with previously published fluid theory predictions of spectral density. ¿ American Geophysical Union 1990