Dr. T. Y. Cao, working under the direction of Professor Schweber, is examining the history of the renormalization program in quantum field theory (QFT), covering the period form the early 1950's to the beginning of the 1980's--that is, from the work of Dyson and Salam that completed the initial phase of the renormalization theory to the formulation of the notion of effective field theories by Weinberg, Georgi and others. Drs. Cao and Schweber hope to demonstrate that with the changing understanding of the physics of renormalization came a new conceptualization of quantum field theory, both with respect to its global structural pattern and to its status as a fundamental or phenomenological framework, thereby providing a basis for the proper understanding of the history of quantum field theory and of elementary particle physics. The emphasis in this research will be on the advances in understanding the physics and the philosophy of renormalization in the context of the interplay between quantum field theory, S-matrix theory and high energy physics, and that of the standard model of electroweak and strong interactions.