For the effective development and optimization of plasma torches and plasma processes a knowledge of the spatial distribution of plasma properties within the generated plasma jets is useful. Information about some of these properties also in case of arbitrary distribution can be achieved by computer tomography (CT) using radiation emitted by the plasma jet. The stationarity of the plasma jet is a necessary condition for the CT technique described in this paper. By CT in principle the radiation from a small cross-sectional disk of the plasma jet is recorded successively under different directions perpendicular to the torch axis. From the recorded data the spatial distribution of radiation emissivity within the jet is calculated using an algebraic recursive algorithm. The CT was applied for the investigation of a TRIPLEX II plasma jet giving the following results: The jet is characterized by a very high degree of stationarity and exhibits a definite triple symmetry, which can be described by three partial plasma jets. Measuring their positions the influence of the arc current on the TRIPLEX plasma jet rotation was determined.