  The neutral kaon system offers a unique possibility to perform fundamental
tests of CPT invariance, as well as of the basic principles of quantum
mechanics. The most recent and significant limits on CPT violation are
reviewed, including the ones related to possible decoherence mechanisms or
Lorentz symmetry breaking, which might be induced by quantum gravity. The
experimental results show no deviations from the expectations of quantum
mechanics and CPT symmetry, while the accuracy in some cases reaches the
interesting Planck scale region. Finally, prospects for this kind of
experimental studies at the upgraded DAFNE e+e- collider at Frascati are
briefly discussed.
