  We have reexamined the problem of $n-\bar n$ oscillations for ultra-cold
neutrons (UCN) confined within a trap. We have shown that the growth of the
$\bar n$ component with time is to a decent accuracy given by $P(\bar n)=
\epsilon^2_{n\bar n} t_Lt,$ where $\epsilon_{n\bar n}$ is the mixing parameter,
$t_L\sim 1 $ sec in the neutron propagation time between subsequent collisions
with the trap walls. Possible corrections to this law and open questions are
discussed.
