  We discuss the relation between the Gell-Mann-Low beta function and the
``flowing couplings'' of the Wilsonian action $S_\L[\phi]$ of the exact
renormalization group (RG) at the scale $\L$. This relation involves the
ultraviolet region of $\L$ so that the condition of renormalizability is
equivalent to the Callan-Symanzik equation. As an illustration, by using the
exact RG formulation, we compute the beta function in Yang-Mills theory to one
loop (and to two loops for the scalar case). We also study the infrared (IR)
renormalons. This formulation is particularly suited for this study since: $i$)
$\L$ plays the r\^ole of a IR cutoff in Feynman diagrams and non-perturbative
effects could be generated as soon as $\L$ becomes small; $ii$) by a
systematical resummation of higher order corrections the Wilsonian flowing
couplings enter directly into the Feynman diagrams with a scale given by the
internal loop momenta; $iii$) these couplings tend to the running coupling at
high frequency, they differ at low frequency and remain finite all the way down
to zero frequency.
