  A model based on the analytic approach to QCD, involving a summation of
threshold singularities and taking into account the nonperturbative character
of the light quark masses, is applied to find hadronic contributions to
different physical quantities. It is shown that the suggested model allows us
to describe well such objects as the hadronic contribution to the anomalous
magnetic moment of the muon, the ratio of hadronic to leptonic $\tau$-decay
widths in the vector channel, the Adler $D$-function, the smeared
$R_\Delta$-function, and the hadronic contribution to the evolution of the fine
structure constant.
