  We report the most recent results from high-resolution numerical simulations
of structure formation in two flat cold+hot dark matter models with neutrino
mass densities $\onu=0.2$ and 0.3. We find that structure forms too late in all
CDM+HDM models with $\onu>0.2$ to account for the amount of dense neutral gas
in high-redshift damped Lyman-$\alpha$ systems. The $\onu=0.2$ model at
$z\approx0$ provides a better match to observations than the pure CDM model.
