  The most general supersymmetric model contains baryon number violating terms
of the form $\lambda_{ijk}\;\ov{D}_i\, \ov{D}_j\, \ov{U}_k$ in the
superpotential. We reconsider the bounds on these couplings, assuming that
lepton number conservation ensures proton stability. These operators can
mediate $n - \ov{n}$ oscillations and double nucleon decay. We show that
neutron oscillations do not, as previously claimed, constrain the
$\lambda_{dsu}$ coupling; they do provide a bound on the $\lambda_{dbu}$
coupling, which we calculate. We find that the best bound on $\lambda_{dsu}$
arises from double nucleon decay into two kaons; the calculation is discussed
in detail. There are no published limits on this process; experimenters are
urged to examine this nuclear decay mode. Finally, the other couplings can be
bounded by the requirement of perturbative unification.
