  We compute the complete electroweak one-loop effect on the process of
$t$-channel single top production at LHC in the Standard Model and in the MSSM
within the mSUGRA symmetry breaking scheme. We find that the one-loop
electroweak SM effect is large, and decreases the cross section of an amount
that is of the same size as that of the NLO QCD one. The genuine SUSY effect in
the mSUGRA scheme, for a general choice of benchmark points, is rather small.
It might become large and visible in more general scenarios around thresholds
involving light stop and neutralino mass values.
