  The recent progress on unquenched QCD simulations is critically reviewed.
After some discussions on problems and subtleties in unquenched simulations,
hadron spectra obtained from both quenched and unquenched simulations are
compared among various gauge and quark actions. It is found that the Edinburgh
plot does not agree in the continuum limit between Wilson and KS quark actions
even in quenched QCD. Dynamical quark effects on hadron spectra, in particular,
on meson masses are then presented for Wilson-type quark actions. Finally
dynamical quark effects on other quantities such as the topological
susceptibility and the flavor-singlet meson mass are discussed.
