Diurnal and semidiurnal oscillations in the stratosphere and mesosphere as revealed by rocket techniques are reviewed in relation to routine M.R.N. launchings, grenade experiments, and diurnal launch series. Height profiles of phase and amplitude are interpreted as a superposition of modes and feature propagating modes of a higher order than the leading diurnal or semidiurnal modes. Such modes vary between different observing dates and often appear as a dominant part of an oscillation. Their excitation and propagation are discussed with reference to water vapour distribution, correspondence between distribution of heat source and structure of mode (in latitude, longitude and height), and damping. Comparisons are made between observed and theoretical diurnal oscillations at high latitude where negative modes predominate and at low latitude where positive modes predominate. The role of the stratopause region of diurnal heating in opposing the tropospherically generated (1, 1) mode of oscillation is discussed and the possible production of variations in heating at the base of the thermosphere is pointed out.