  Using resummation in perturbation theories at finite temperature or in
non-equilibrium is unavoidable to obtain consistent results. Resummation,
however, is often in conflict with renormalization. In this talk we give two
possible solutions to problems of this type in static resummation. One is the
use of auxiliary finite temperature UV divergent counterterms. The other is to
use a renormalization scheme fitted to the environment. We also suggest a way
how one could proceed in case of dynamic resummations.
