  We have calculated the pressure and energy density in four-flavour QCD using
improved fermion and gauge actions. We observe a strong reduction of finite
cut-off effects in the high temperature regime, similar to what has been noted
before for the SU(3) gauge theory. Calculations have been performed on
$16^3\times 4$ and 16^4 lattices for two values of the quark mass, $ma = 0.05$
and 0.1. A calculation of the string tension at zero temperature yields a
critical temperature $T_c/\sqrt{\sigma} = 0.407 \pm 0.010$ for the smaller
quark mass value.
