Preface; Notation; 1. Free fields in vacuum; 2. Spontaneous symmetry breaking; 3. Chiral perturbation theory; 4. Thermal propagators; 5. Thermal Perturbation Theory; 6. Thermal parameters; 7. Two-loop results; 8. Heavy ion collisions; 9. Non-equilibrium processes; Appendix A. General fields; Appendix B. Global symmetries; Appendix C. Exponential operator; Appendix D. Propagator at origin of coordinates; Appendix E. Reaction rates in vacuum and medium; Appendix F. Coupling constants; Appendix G. Imaginary time method; Appendix H. Quark condensate from partition function; Appendix I. Quark condensate from density expansion; Index.