2026-07-072026-07-07http://salesiana.dossiersoluciones.com/handle/123456789/56690We review the PCT-theorem and problems connected with its demonstration. We add a new proof of the PCT-theorem in the theory of local observables which is similar to that one of Jost in Wightman quantum field theory. We also look at consequences in case the PCT-symmetry is given on the algebraic level. At the end we present some examples which answer general questions and throw some light on open problems.Mathematical PhysicsHigh Energy Physics - Theory81T05, 46L10text