Analytic expressions have been found for the profile of non-linear stable drift waves in a collisionless anisothermal plasma, and also for the relationship of the wave velocity to the wave amplitude. It is shown that the nature of the nonlinear waves (compression or rarefaction) depends substantially on the type of electron distribution function. The wave amplitude is assumed to be small, but finite. For the distribution function closest to the Maxwellian, the nature of the wave is determined by the parameter η = d ln T/d ln n.