  The inferred values of the cosmological baryon and dark matter densities are
strikingly similar, but in most theories of the early universe there is no true
explanation of this fact; in particular, the baryon asymmetry and thus density
depends upon unknown, and {\it a priori} unknown and possibly small,
CP-violating phases which are independent of all parameters determining the
dark matter density. We consider models of dark matter possessing a
particle-antiparticle asymmetry where this asymmetry determines both the baryon
asymmetry and strongly effects the dark matter density, thus naturally linking
$\Omega_{\rm{b}}$ and $\Omega_{\rm{dm}}$. We show that sneutrinos can play the
role of such dark matter in a previously studied variant of the MSSM in which
the light neutrino masses result from higher-dimensional supersymmetry-breaking
terms.
