  I illustrate a general formalism based upon the subtraction method for the
calculation of next-to-leading order QCD cross sections for any number of jets
in any type of hard collisions. I discuss the implementation of this formalism
in a numerical program which generates partonic kinematical configurations with
an appropriate weight, thus allowing the definition of arbitrary jet algorithms
and cuts matching the experimental setup at the last step of the computation. I
present results obtained with computer codes which calculate one-jet and
two-jet inclusive quantities in photon-hadron and hadron-hadron collisions.
