  The neutrinoless double $\beta$-decay is reviewed. Model independent evidence
in favor of neutrino masses and mixing is briefly summarized. The data of the
recent experiments on the search for $0\nu\beta\beta$-decay are presented and
some future experiments are discussed. The possible values of the effective
Majorana mass, which can be predicted on the basis of the neutrino oscillation
data under different assumptions on the pattern of the neutrino mass spectrum,
are considered. A possible model independent test of the nuclear matrix element
calculations is discussed.
