  Understanding the pattern of gluon radiation in $t \bar t$ production and
decay processes is important for making an accurate determination of the top
mass from the momenta of its decay products. The larger energy of the LHC $pp$
collider boosts the top cross section by a factor of 100 compared to that at
the Tevatron, but it also increases the amount of additional gluon radiation.
We calculate the cross section for gluon radiation in top production and decay
at the LHC. The distributions of this radiation are presented and the exact
matrix-element results are compared with results from the HERWIG parton-shower
Monte Carlo.
