Résumé
We discuss how symmetry non restoration arises in multi scalar field theories at finite temperatures and present its consequences for a relativistic Higgs multi sector as well as for a non-relativistic model of hard core spheres. For the former, it is known that temperature effects on the couplings do not alter, qualitatively, the phase transition pattern. For the second model we show that symmetry non restoration cannot take place, at high temperatures, when the important temperature dependence of the couplings is considered.