  Seesaw mechanism has been a dominant paradigm in the discussion of neutrino
masses. I discuss how this idea can be tested via a baryon number violating
process such as $N-\bar{N}$ oscillation. Since the expected seesaw scale is
high and the $N-\bar{N}$ amplitude goes like $M^{-5}_{R}$, one might think that
this process is not observable in realistic seesaw models for neutrino masses.
In this talk I show that in supersymmetric models, the above conclusion is
circumvented leading to an enhanced and observable rate for $N-\bar{N}$
oscillation. I also discuss a new mechanism for baryogenesis in generic models
for neutron-anti-neutron oscillation and show how the requirement of adequate
baryogenesis can put an upper limit on the neutron-anti-neutron oscillation
time.
