A set of ground-based spectroscopic observations of the [SII> 6716 ¿, 6731 ¿ emission from the Io plasma torus (IPT) is described. The Doppler-resolved spectra show that the perpendicular ion temperature increases significantly with increasing distance from the plasma equator at 6.0 RJ. Using a simple model, a Kappa-distribution of form similar to that used previously in an analysis of electron temperature dependence with magnetic latitude [Meyer-Vernet et al., Icarus, 116, 202, 1995> provides a reasonable fit to our data. It is also shown that the ion temperature (Ti) measured by the Voyager 1 plasma sciences experiment (PLS) can be successfully modelled with the derived parameters, assuming an L-8/3 fall-off of Ti with distance along the plasma equator which is consistent with previous ground-based and spacecraft measurements. The results suggest that extrapolation of PLS measurements assuming two overlapping Maxwellian distributions with constant temperatures along magnetic field lines to construct 3-D models of the IPT need to be re-assessed.¿ 1997 American Geophysical Union