  We review our attempt at understanding the phase structure of lattice QCD
with the Wilson fermion formulation at finite temperature, based on a
spontaneous breakdown of parity-flavor symmetry. Numerical results
demonstrating explicitly the spontaneous breakdown of parity-flavor symmetry
beyond the critical line at both zero and finite temperatures are reported. The
phase structure and order of the chiral transition are reported for $N_f=2$,3,
and 4 flavors, and the approach towards the continuum limit is discussed.
