Measurements of externally excited moving striations in a low‐pressure (0.005‐0.03 Torr) argon discharge are presented. The wave propagates with little radial structure, and corresponds to the lowest radial mode. A theory which uses the Boltzmann equation for the electron motion, and fluid equations for the ions gives results in agreement with the experiment. Included in this model are the effects of ion inertia, and of depletion of the high‐energy tail of the electron distribution function due to loss of electrons to the tube walls. Results indicate that both effects are important at low pressure. A simple model, which uses fluid equations for electrons and ions, shows the relationship between moving striations and ion acoustic waves.