  We present updated NLO predictions for the electroweak t-channel production
of heavy quarks at the Tevatron and at the LHC. We consider production of
single top and fourth generation t' starting from both 2 to 2 and 2 to 3 Born
processes. Predictions for tb' and t'b' cross sections at NLO are also given
for the first time. A thorough study of the theoretical uncertainties coming
from parton distribution functions, renormalisation and factorisation scale
dependence and heavy quark masses is performed.
