  This paper is a mini-review of the atmospheric muon and neutrino flux
calculations based upon a recent version of CORT code and up-to-date data on
primary cosmic rays and hadronic interactions. A comparison of calculations
with a representative set of atmospheric muon data for momenta below 1 TeV/c is
presented. The overall agreement between the calculated muon fluxes and the
data provides an evidence in favor of the validity of adopted description of
hadronic interactions and shower development. In particular, this supports the
low-energy atmospheric neutrino fluxes predicted with CORT which are
essentially lower than those used in current analyses of the sub-GeV and
multi-GeV neutrino induced events in underground neutrino detectors.
