Particle physics, cosmology and astrophysics constraints on neutrino masses, oscillations and decays

We review the properties of neutrinos, especially their masses decays and mixing angles, from the points of view of particle physics, astrophysics and cosmology. Constraints imposed by the standard model of cosmology and the standard model of particle physics, as well as experimental constraints from solar neutrino experiments, neutrino oscillations and other particle physics experiments are analysed. We consider several possible scenarios for the values of neutrino masses. A favorite solution raises the possibility that the tau-neutrino is the main component of the dark matter of the universe and that MSW oscillations between the mu-neutrino and the electron neutrino are responsible for the small solar neutrino signal observed. We discuss experimental ways of testing this hypothesis.