In August 2013, the U.S. Government Accountability Office (GAO) issued a report, for which they performed a required study on patent litigation. The study aimed to find out what was known about the extent and characteristics of patent litigation; to survey knowledgeable stakeholders about factors influencing patent litigation; to identify judicial developments that could impact patent litigation; and to examine actions taken by the United States Patent and Trademark Office (USPTO or Office) that could affect future patent litigation. The report concluded with a recommendation that the Secretary of Commerce direct the Director of PTO to consider examining trends in patent infringement litigation, including the types of patents and issues in dispute, and to consider linking this information to internal data on patent examination to improve the quality of issued patents and the patent examination process. The USPTO agreed that it would be appropriate to undertake an investigation of trends in patent infringement litigation, and to consider how any trends discovered could potentially be linked to its own internal patent examination data. The USPTO further agreed that it would be appropriate to consider whether the results of the investigation could be used to support its ongoing efforts to improve the patent examination process, and ultimately the quality of issued patents. In addition, the USPTO chose to include inter partes review (IPR) proceedings in the study, with the goal of gaining additional insights that could lead to enhanced patent quality. The USPTO carried out the investigation as recommended by GAO, and this book details the methodology and results.