Electrostatic probe measurements for low-pressure inductively coupled SF6 plasmas are performed. From the current-voltage (I-V) curves of the probe, the saturation currents of the positive ions, the electron density, and the electron temperature are measured. The electronegativity and the positive ion density are obtained by several different methods (the ion saturation current at the floating potential, the positive and negative current balances at the floating potential, and the three pressure point method). They are compared with the positive ion density obtained by the orbital-motion-limited theory. (C) 2010 Elsevier B.V. All rights reserved.