We report on recent calculations in perturbative Quantum Chromodynamics (QCD) and its generalization to Yang-Mills theories with fermions. We summarize the present status of four-loop calculations of the splitting functions for the scale dependence (evolution) of the quark and gluon distributions of hadrons. Five-loop results are presented for the beta function, i.e., the running of the coupling constant, and for hadronic decays of the Higgs boson.