A recently presented concept, where, in the framework of parametrized relativistic quantum field theory, antiparticles are described consistently with negative frequencies, but positive energy density, is used to analyse the decay of neutralK-mesons, where the experimental results usually are interpreted as an evidence forCP-violation. In the theory presented the charge conjugation is antilinear, as in original Dirac theory, and theCPT-transformation is unitary. The Hamiltonian is indefinite, and changes sign under theCPT-transformation, since positive and negative eigenvalues are interchanged. As a result the eigenstates of the Hamiltonian are notCPT-eigenstates. The interference of positive and negative frequencies leads to a mixing ofCPT-eigenstates, as is observed in experiment. The study of a simple model system shows that the proposed mechanism of dynamical mixing offers an explanation for the experiments on theK 0− $$\bar K$$ 0-meson system, with respect to both the observed mixing of eigenstates and the observed difference in the number of “CP-violating” events in the decays of the longer and shorter living neutralK-mesonsK L andK S . No symmetry violation of the theory needs be assumed.