  We investigate the phase structure of lattice QCD for general number of
flavors $N_F$. Based on numerical results combined with the result of the
perturbation theory we propose the following picture: When $N_F \ge 17$, there
is only a trivial fixed point and therefore the theory in the continuum limit
is trivial. On the other hand, when $16 \ge N_F \ge 7$, there is a non-trivial
fixed point and therefore the theory is non-trivial with anomalous dimensions,
however, without quark confinement. Theories which satisfy both quark
confinement and spontaneous chiral symmetry breaking in the continuum limit
exist only for $N_F \le 6$.
