The plasma of a hollow cathode arc discharge (argon/titanium) was studied by emission spectroscopy and probe measurements. The behavior of the relative particle concentrations of the different heavy plasma components as well as the concentration and temperature of the electrons was determined as function of the vertical distance from the anode crucible.Abel-inverted radial distributions of the relative level populations for Ti Z (neutral titanium), Ti IZ (singly ionized titanium), Ar Z and AT ZZ are presented. Further measurements characterize the influence of the discharge current on the relative level population.