This book will explore the implications of congressional oversight of homeland security, specifically the Department of Homeland Security (DHS). Oversight of DHS has been extensively researched since the 9/11 Commission recommended that it be reformed. This book argues that much of the previous research into this topic relied on a limited view of oversight and used a limited set of tools to measure it. This work reviews the existing literature on homeland security oversight and offers alternative ways of measuring oversight. It conducts two case studies to establish a more complete view of homeland security oversight. Then, it quantitatively analyzes legislative data and offers a new approach to using agency interactions to provide a more meaningful picture of homeland security oversight. Finally, the book offers recommendations based on the conclusions of the research to achieve optimal congressional oversight of homeland security.