Both high and low temperature effects in QCD will be discussed in the seminar. At high temperature, much higher than the deconfinement phase transition, chromoelectric fields are screened in a quark-gluon plasma. These thermal screening effects can be taken into account by resumming an infinite number of Feynman diagrams, the so-called hard thermal loops (HTL's). Several different approaches to obtain the HTL effective action will be shown. Finally, using chiral Lagrangian techniques, low temperature effects in QCD will be discussed.