  The search for neutrinoless double beta decay and WIMP dark matter has a
broad potential to test particle physics beyond the standard model. During the
last years, the analysis of various contributions to the double beta decay rate
by the Heidelberg group led, besides the most restrictive limit on the
effective Majorana neutrino mass, to bounds on left-right-symmetric models,
leptoquarks and supersymmetry. In a general framework bounds on arbitrary
lepton number violating theories can be derived. Using double beta technology
for direct dark matter detection, stringent limits on the spin-independent
WIMP--nucleon interaction have been obtained. These results deduced from the
Heidelberg-Moscow double beta decay experiment are reviewed. Also an outlook on
the future of double beta decay and dark matter search, the GENIUS proposal, is
given.
