  We discuss the structure of infrared singularities in on-shell QCD amplitudes
at two-loop order. We present a general factorization formula that controls all
the $\ep$-poles of the dimensionally regularized amplitudes. The dependence on
the regularization scheme is considered and the coefficients of the $1/\ep^4,
1/\ep^3$ and $1/\ep^2$ poles are explicitly given in the most general case. The
remaining single-pole contributions are also explicitly evaluated in the case
of amplitudes with a $q{\bar q}$ pair.
