Phase Transition Critical Flavor Number of QCD

We present an entirely perturbative QCD determination of the critical phase transition flavor number $N_f^{cr}$ of QCD. The results obtained are compared with various determinations of $N_f^{cr}$ by non-pertrubative methods, including lattice QCD. The wider physics implication of the existence of the Banks-Zaks regime of QCD with only weakly interacting quarks, is discussed briefly.