The equilibrium chemical composition and the thermodynamic properties of argon plasmas have been calculated for five pressures (0.1, 0.5, 1.0, 2.0, and 5.0 atm) at 100 K deg increments for the temperature range 5000° to 35 000°K. The argon plasma is assumed to be a perfect gas complex consisting of six components, namely electrons, argon atoms, and the first four argon ions. The partition functions for these have been calculated using tabulated data for observed atomic energy levels and estimated energies for energy levels which are predicted although not observed. The partition functions were terminated by application of the Debye cutoff criterion and a corresponding lowering of the ionization potential was included. The calculated data are presented in graphical form and the method followed in calculating the partition functions is evaluated.