  We consider field theory formulation for directed polymers and interfaces in
the presence of quenched disorder. We write a series representation for the
averaged free energy, where all the integer moments of the partition function
of the model contribute. The structure of field space is analysed for polymers
and interfaces at finite temperature using the saddle-point equations derived
from each integer moments of the partition function. For the case of an
interface we obtain the wandering exponent $\xi= (4-d)/2$, also obtained by the
conventional replica method for the replica symmetric scenario.
