  Assuming 3-neutrino mixing and massive Majorana neutrinos, we present some
implications of the neutrino oscillation solutions of the solar and atmospheric
neutrino problems and the results of the CHOOZ experiment for the predictions
of the neutrinoless double-beta decay rate. If the present or upcoming searches
of neutrinoless double-beta decay give a positive result, the Majorana nature
of massive neutrinos will be established. From the determination of the value
of the effective Majorana mass, it would be possible to obtain information on
the neutrino mass spectrum. With additional information on the absolute value
of neutrino masses, it might be possible to infer if CP-parity is violated in
the lepton sector.
