Using a Systems Theory approach allows a person to analyze the intertwined elements of the drug development system and the potential influences of the environment. Thomas Hughes's Large Technological Systems (LTS) Theory is one that could be used for this purpose; however, it falls short in its ability to address the complexity of current day regulatory environments. This dissertation provides a critical analysis of Hughes's LTS Theory and his phases of evolution as they apply to the United States (U.S.) system for biologic drug research, development and labeling. It identifies and explains potential flaws with Hughes's LTS Theory and provides suggested improvements. As an alternative approach, this dissertation explores the concept of "techno-regulatory system" where government regulators play an integral part in system innovations and explains why such systems do not always follow Hughes's model. Finally, this dissertation proposes a hybrid version of Hughes's systems approach and uses it to explain the changes that occurred in the drug approval system in response to the push for, opposition, and inclusion of, pediatric research in drug development during the period 1950-2003. / Ph. D.