  A review of baryon and lepton conservation in supersymmetric grand unified
theories is given. Proton stability is discussed in the minimal SU(5)
supergravity grand unification and in several non-minimal extensions such as
the $SU(3)^3$, SO(10) and some string based models. Effects of dark matter on
proton stability are also discussed and it is shown that the combined
constraints of dark matter and proton stability constrain the sparticle
spectrum. It is also shown that proton lifetime limits put severe constraints
on the event rates in dark matter detectors. Future prospects for the
observation of baryon and lepton number violation are also discussed.
