1.The Klein-Gordon and Dirac equations and the interpretation of their negative-energy solutions. 2.The electromagnetic interactions of spin-0 particles. 3.The electromagnetic interactions of spin ½ particles. 4.Deep inelastic electron-nucleon scattering and quark Parton model. 5.Introduction to weak interactions. 6.The hadronic weak current and neutral currents. 7.Difficulties with weak interaction phenomenology. 8.Gauge invariance as a dynamical principle. 9.Hidden gauge invariance. 10.An introduction to quantum chromodynamics. 11.The Glashow-Salam-Weinberg gauge theory of electroweak interactions. 12.Four last things.