The measurement of the surface tension of liquid silicon has a long history with many results but no general agreement between them. Two values at the melting temperature are cited in reviews (749 and 827mN/m [N. Eustathopoulos, E. Ricci, B. Drevet, Note Technique DEM No. 97/58, CEA, 1997]) but there are few arguments to determine the correct one. In the present study, new data for the surface tension obtained with the analysis of characteristic frequencies of a levitating drop are presented. The effect of oxygen and nitrogen are also considered. These data are compared with former data obtained with contactless techniques. The most recent surface tension values obtained with drop weights ranging on two orders of magnitude and environments of different natures (argon, hydrogen and vacuum) show excellent agreement (within a 1.5% margin) at temperatures between 1350K and 2400K. The comparison of these data to others obtained with different techniques, reveal a good agreement, except those obtained with the sessile drop technique on some supports like BN, SiO 2 and MgO. However, these special cases may be connected with the reactivity of silicon with these supports.