  The NLO Brodsky-Lepage-Mackenzie (BLM) scale for the pion transition form
factor has been determined. To achieve that, a consistent calculation up to
nf-proportional NNLO contributions to both the hard-scattering amplitude and
the perturbatively calculable part of the pion distribution amplitude has been
performed. By combining and matching the results obtained for these two
amplitudes, a proper cancellation of collinear singularities has been
established and the gamma5 ambiguity problem (related to the use of the
dimensional regularization method) has been resolved by using the naive-gamma5
as well as the 't Hooft-Veltman (HV) schemes. It has been demonstrated that the
prediction for the pion transition form factor is independent of the
factorization scale muF at every order in the strong coupling constant, making
it possible to use the simplest choice muF^2=Q^2 at the intermediate steps of
the calculation. Assuming the pion asymptotic distribution amplitude and
working in the \bar{MS} scheme, we have found the BLM scale to be muR^2=muBLM^2
~ Q^2/9. Based on the same distribution, the complete NLO prediction for the
pion transition form factor has been calculated in the alphaV definition of the
QCD coupling renormalized at muR^2=muV^2 = e^{5/3} muBLM^2 ~ Q^2/2. It is in
good agreement with the presently available experimental data.
