Lepton fluxes from atmospheric charm

We reexamine the charm contribution to atmospheric lepton fluxes in the context of perturbative QCD. We include next-to-leading order corrections and discuss theoretical uncertainties due to the extrapolations of the gluon distributions at small {ital x}. We show that the charm contribution to the atmospheric muon flux becomes dominant over the conventional contribution from {pi} and {ital K} decays at energies of about 10{sup 5} GeV. We compare our fluxes with previous calculations. {copyright} {ital 1999} {ital The American Physical Society}