  We discuss the final results of the MACRO experiment on atmospheric neutrino
oscillations. The data concern event topologies with average neutrino energies
of ~3 and ~50 GeV. Multiple Coulomb Scattering of the high energy muons was
used to estimate the neutrino energy event by event. The angular distributions,
the L/E_nu distribution, the particle ratios and the absolute fluxes all favor
nu_mu --> nu_tau oscillations with maximal mixing and Delta m^2 ~0.0023 eV^2.
Emphasis is given to measured ratios which are not affected by Monte Carlo (MC)
absolute normalization; a discussion is made on MC uncertainties. A preliminary
search for possible Lorentz invariance violation contributions to atmospheric
neutrino oscillations is presented and discussed.
