Petcov, Serguey T.20052011-09-0720052011-09-072005Phys. Scr. T121 (2005) 94-101https://openscience.sissa.it/handle/1963/1743The compelling experimental evidences for oscillations of solar and atmospheric neutrinos imply the existence of 3-neutrino mixing in vacuum. We briefly review the phenomenology of 3-v mixing, and the current data on the 3-neutrino mixing parameters. The open questions and the main goals of future research in the field of neutrino mixing and oscillations are outlined. The predictions for the effective Majorana mass |<m>| in (betabeta)0v-decay in the case of 3-v mixing and massive Majorana neutrinos are reviewed. The physics potential of the experiments, searching for (betabeta)0v-decay and having sensitivity to |<m>| >~ 0.01 eV, for providing information on the type of the neutrino mass spectrum, on the absolute scale of neutrino masses and on the Majorana CP-violation phases in the PMNS neutrino mixing matrix, is discussed.281157 bytesapplication/pdfen-USPreprint