  The generalization of Density Matrix Renormalization Group (DMRG) approach as
implemented in quantum chemistry, to the case of non-orthogonal orbitals is
carefully analyzed. This generalization is attractive from the physical point
of view since it allows a better localization of the orbitals. The possible
implementation difficulties and drawbacks are estimated. General formulae for
hamiltonian matrix elements useful in DMRG calculations are given.
