  A microscopic calculation of the equation of state for asymmetric nuclear
matter is presented. We employ realistic nucleon-nucleon forces and operate
within the Dirac-Brueckner-Hartree-Fock approach to nuclear matter. The focal
point of this paper is a (momentum-space) G-matrix which properly accounts for
the asymmetry between protons and neutrons. This will merge naturally into the
development of an effective interaction suitable for applications to asymmetric
nuclei, which will be the object of extensive study in the future.
