We investigate in the framework of linear kinetic theory the effect of neutrals on plasma oscillations generated by drift of the electrons in a boundless, stationary, homogeneous, Maxwellian plasma. It is assumed that collisions between charged particles and neutrals are dominant with respect to collisions between charged particles. The expected stabilizing effect of these collisions on the critical velocity and growth rate is confirmed and evaluated. Our results reduce to those of Klevans and Primack—the most accurate results to date for ion and electron plasma waves—in the collisionless, driftless case; to those of Bernstein and Kulsrud (with somewhat improved accuracy) in the collisionless case; and to those of Kadomtsev in the case of very high electron–ion temperature ratios and [Formula: see text], the wave number corresponding to the electron Debye length.