Congress has recently demonstrated significant ongoing interest in litigation by "patent assertion entities" (PAEs), which are colloquially known as "patent trolls" and sometimes referred to as "non-practising entities" (NPEs). The PAE business model focuses not on developing or commercialising patented inventions but on buying and asserting patents, often against firms that have already begun using the claimed technology after developing it independently, unaware of the PAE patent. PAEs include not only free-standing businesses but patent holding subsidiaries, affiliates, and shells of operating companies that want to participate in the PAE industry and/or a new means of countering competitors. The proliferation of PAEs was among the central factors raised in support of the most recent patent reform legislation, the Leahy-Smith America Invents Act of 2011 (AIA). However, the AIA contains relatively few provisions that arguably might impact PAEs, apparently because of lively debate over what, if anything, should be done about them. In the 113th Congress, the Saving High-Tech Innovators from Egregious Legal Disputes (SHIELD) Act of 2013 (H.R. 845) has been introduced in an effort to affect the number of lawsuits filed by PAEs. This book reviews the current debate and controversy surrounding PAEs and their effect on innovation, examines the reasons for the rise in PAE litigation, and explores the legislative options available to Congress if it decides that these are issues that should be addressed.