Breaking of CPT and Lorentz symmetries

CPT symmetry rests on very solid foundations of quantum field theory: Lorentz symmetry, correspondence of spin and statistics, and locality. I describe how violation of CPT and Lorentz symmetries may result from new infrared degrees of freedom, which also lead to the change of coupling constants in time and new long-range interactions. I motivate the effective field theory description of CPT violation, and determine its magnitude suggested by the observable size of the matter-antimatter asymmetry.