  In the talk the leading four-loop contribution to the beta-function of the
strong coupling in the SM is discussed. Some details of calculation techniques
are provided. Special attention is paid to the ambiguity due to utilized
$\gamma_5$ treatment and a particular prescription with anticommuting
$\gamma_5$ is advocated. As a by-product of our computation the four-loop
beta-function in QCD with "gluino" is also obtained.
