Abstract: We have studied a high- (ultrahigh-) pressure short-arc discharge in xenon with thoriated tungsten cathodes. A system of equations formulated based on earlier experimental data indicating possible emission of cathode material (thorium) into the discharge gap has made it possible to determine the electric field strength, plasma temperature, and concentration of thorium atoms as well as thorium and xenon ions in the plasma. The problem has been solved for a model discharge between planar electrodes. The results indicate the key role of thorium atoms in the cathode region. Thorium atoms determine the ionization balance and other electrokinetic properties of plasma. Emission of thorium atoms reduces the plasma temperature at the cathode, which turns out to be noticeably lower than the plasma temperature near the anode; this is a new result that agrees with experimental data. Other electrokinetic characteristics of the plasma (in particular, charged particle concentration and electric field strength) are also in good agreement with the experiment.