This Handbook has three objectives: 1) to serve as a primer for explaining the complex issues around the use of electromagnetic spectrum; 2) to analyze, from both an economic and a legal perspective, the regulatory processes being considered or underway to reallocate or change the use of spectrum bands; and 3) to be a reference source for industry professionals. Part I of the Handbook provides an overview of the spectrum and the regulatory process. Part II of the Handbook explains the various available spectrum bands, discussing their range, location, and physical properties and how these impact their ability to be used. Part III of the Handbook explains valuation issues. Part IV contains an international comparative analysis of spectrum regulation and allocation. An analysis of the current allocation of these spectrum bands in the United States follows. Part IV contains detailed explanations of the various spectrum band plans. Throughout the Handbook, we provide links in the footnotes to sources for additional information.