Lorentz symmetry is a basic ingredient of the standard Model of particles physics However, several authors have argued that at high energies Lorentz symmetry and possibly CPT could be broken The Lorentz violating parameters of the Standard Model (Colladay-Kostelecky) extended in the power-counting renormalizable sector have been measured with great precision It turns out that Lorentz symmetry is a very precise symmetry of Nature, at least in low-energy domain Several(dimensionless)parameters have bounds d11￠Lorentz symmetry is a basic ingredient of the Standard Model of particles physics. However, several authors have argued that at high energies Lorentz symmetry and possibly CPT could be broken. The Lorentz violating parameters of the Standard Model (Colladay-Kostelecky) extended in the power-counting renormalizable sector have been measured with great precision. It turns out that Lorentz symmetry is a very precise symmetry of Nature, at least in low-energy domain. Several (dimensionless) parameters have bounds 15 30 1040 10, 10, − − −