  We report on results of a target of opportunity observation of the X-ray
transient XTE J1118+480 performed on 2000 April 14-15 with the Narrow Field
Instruments (0.1-200 keV) of the SAX satellite. The measured spectrum is a
power law with a photon index of ~1.7 modified by an ultrasoft X-ray excess and
a high-energy cutoff above ~100 keV. The soft excess is consistent with a
blackbody with temperature of ~40 eV and a low flux, while the cut-off power
law is well fitted by thermal Comptonization in a plasma with an electron
temperature of 100 keV and an optical depth of order of unity. Consistent with
the weakness of the blackbody, Compton reflection is weak. Though the data are
consistent with various geometries of the hot and cold phases of the accreting
gas, we conclude that a hot accretion disk is the most plausible model. The
Eddington ratio implied by recent estimates of the mass and the distance is
about 10^{-3}, which may indicate that advection is probably not the dominant
cooling mechanism. We finally suggest that the reflecting medium has a low
metallicity, consistent with location of the system in the halo.
