  We derive general tree-level recursion relations for amplitudes which include
massive propagating particles. As an illustration, we apply these recursion
relations to scattering amplitudes of gluons coupled to massive scalars. We
provide new results for all amplitudes with a pair of scalars and n < 5 gluons.
These amplitudes can be used as building blocks in the computation of one-loop
6-gluon amplitudes using unitarity based methods.
