We discuss how to compute one-loop amplitudes in QCD by combining unitarity in higher dimensions with tree level recursion relations. We present results for all N-gluon one-loop amplitudes for arbitrary helicities. We show that the algorithm has a mild, polynomial growth in N and demonstrate the numerical stability of the results. Finally, we discuss the extension to more general LHC processes involving quarks and vector bosons, in particular we present new results for W+3jets, which is an omnipresent background in new physics searches at the LHC known up to now only at leading order.