This paper describes experimental measurements of flow velocity, electron temperature, and density performed in a steady, rarefied, free jet of argon plasma. The plasma jet is generated by an arc discharge. The axial profiles of the flow velocity, electron temperature and density, and ion saturation currents are determined over a length of 60 cm starting from the nozzle exit. The radial profiles of these quantities are measured in the subsonic zone of the plasma flow. The electron temperature and density are deduced from the characteristic of a single, cylindrical electrostatic probe. The experimental conditions are such that the Debye length &lgr;D ≪ probe diameter &fgr; ≪ mean free path. The velocity of the flowing plasma is determined from the ion saturation currents of two mutually perpendicular probes. The method of Kanal is used without a correction factor on the ion current collected by the perpendicular probe.