  The neutrinoless double beta decay is analyzed using a general Lorentz
invariant effective Lagrangian for various decaying nuclei of current
experimental interest: $^{76}$Ge, $^{82}$Se, $^{100}$Mo, $^{130}$Te, and
$^{136}$Xe. We work out the half-lives and angular correlation coefficients of
the outgoing electrons in several scenarios for new physics: the left-right
symmetric models, the R-parity-violating SUSY and models with leptoquarks. The
theoretical uncertainty in the nuclear matrix elements is discussed.
