  We study QCD radiation in decay processes involving heavy particles. As
input, the first-order gluon emission rate is calculated in a number of
reactions, and comparisons of the energy flow patterns show a non-negligible
process dependence. To proceed further, the QCD parton shower language offers a
convenient approach to include multi-gluon emission effects, and to describe
exclusive event properties. An existing shower algorithm is extended to take
into account the process-dependent mass, spin and parity effects, as given by
the matrix element calculations. This allows an improved description of
multiple gluon emission effects off b and t quarks, and also off nonstandard
particles like squarks and gluinos. Phenomenological applications are presented
for bottom production at LEP, Higgs particle decay to heavy flavours, top
production and decay at linear colliders, and some simple supersymmetric
processes.
