Theoretical and Phenomenological Aspects of CPT Violation

I review briefly various models and ways of Quantum-Gravity induced CPT violation, and discuss in some detail their phenomenology, in particular precision CPT tests in neutral mesons, and hydrogen/antihydrogen spectroscopy. As I shall argue, severe constraints can be placed in CPT violating parameters, with sensitivities that can safely exclude models with effects suppressed by a single power of Planck mass.