The Theoretical Elementary Particle Physics group acknowledges that the fundamental task of physics is to learn the rules of the basic interactions governing the behavior of matter and to search for new laws when present knowledge fails to answer the remaining mysteries of the observable universe. At the foundation of modern theories of particle physics is a deep and beautiful symmetry principle: the invariance of physical laws under symmetry transformations at every space-time point. Theories that show this symmetry are known as Yang-Mills or Gauge Theories. The Standard Model of Strong, Electromagnetic and Weak interactions is the most successful of these theories. It describes all known interactions of matter except gravity.<br>The Electroweak part of the Standard Model is being tested to a high degree of precision. The Strong interaction part, the Quantum Chromodynamics (QCD) Theory, which describes the interactions among the quarks, is being closely scrutinized, both perturbatively and nonperturbatively. The Standard Model is incomplete, however, since a number of fundamental puzzles, such as CP violation and the origin of masses, remain unsolved. The solutions to these problems probably lie outside the framework of the Standard Model. Students admitted to the Ph.D. program are supported financially either by teaching and research assistantships or fellowships. Research leading to the dissertation can be carried out not only within the Department of Physics, but, with appropriate arrangements, either partly or entirely at other locations. Recent dissertation research has been carried out at various national laboratories across the globe, such as the NIST Center for Neutron Research, Jefferson Lab, Fermilab, CERN, and the Paul Scherrer Institute.