  The NEMO collaboration is presently mounting the NEMO-3 detector in the
Fr\'ejus Underground Laboratory. This detector, which will be completed by the
end of the year 2000, is devoted to the search of neutrinoless double beta
decay with various isotopes. Much attention has been focused on ^{100}Mo and
^{82}Se with their large Q_{\beta\beta}-values. The detector is based on the
direct detection of the two electrons by a tracking device and on the
measurement of their energies by a calorimeter. The aim of the experiment is to
have a sensitivity for the effective neutrino mass on the order of 0.1 eV. The
status and the expected performance of the NEMO-3 detector for both internal
and external background rejections and for signal detection are presented.
