The axial distributions of electrons, atomic and molecular ions as well as metastable atoms in an argon ultrahigh frequency (UHF) discharge at a moderate pressure sustained by a traveling electromagnetic wave have been theoretically obtained. The dependence between the absorbed wave power and the electron density necessary for plasma modeling has been numerically derived by taking into account both direct and step‐wise ionization processes. The inclusion of step‐wise ionization process leads to a lower electron temperature comparing to that calculated under the assumption that only the direct ionization takes place. The results have been compared with the experimental data for an UHF argon plasma at 1.8 Torr. A better agreement is achieved when the ionization by metastable–metastable collisions is taken into account together with the step‐wise ionization. ©1996 American Institute of Physics.