  Asymptotic behavior of distribution functions of local quantities in
disordered conductors is studied in the weak disorder limit by means of an
optimal fluctuation method. It is argued that this method is more appropriate
for the study of seldom occurring events than the approaches based on nonlinear
$\sigma$-models because it is capable of correctly handling fluctuations of the
random potential with large amplitude as well as the short-scale structure of
the corresponding solutions of the Schr\"{o}dinger equation. For two- and
three-dimensional conductors new asymptotics of the distribution functions are
obtained which in some cases differ significantly from previously established
results.
