MACRO can detect three topologies of neutrino induced events, corresponding to different parent neutrino energies. The most numerous sample is made of upward throughgoing muons induced by atmospheric neutrinos of average energy 100 GeV. We have observed less events than expected events and the observed zenith distribution does not fit the expected one in the no-oscillation hypothesis, giving a maximum probability of 0.1 percent. Considering the neutrino (numu-nutau) oscillation hypothesis the best probability (17 percent) is obtained for maximum mixing and difference of square masses of a few times 10-3 eV2. The other detected samples are due to internally produced events and upward-going stopping muons, corresponding to an average neutrino energy of around 4 GeV. The results concerning these lower energy sample show a deficit and a shape of the angular distributions in agreement with that predicted by the oscillation model suggested by the higher energy sample. No evidence of a neutrino signal due to dark matter particles in the direction of the core of the Earth and of the Sun has been found among the background due to atmospheric neutrinos and limits have been set. The neutralino hypothesis is investigated and limits on its mass are given.