Chapter 5 turns to patent infringement. It introduces a fundamental tension between patent holders and good faith users of the technology. 3D printing will expose unsuspecting individuals and 3D print shops to patent infringement liability when they print patented objects. To spare unintentionally infringing individuals and 3D print shops the ruinous costs of litigation, I explore options for exemptions and safe harbors. At the same time, if 3D printing enables massive, individualized manufacturing, and if the law exempts each individual act of infringement, patent rights would be eviscerated. Squaring this circle will not be easy, but the chapter explores ways to alleviate the tension, particularly by strengthening indirect infringement claims and limiting exemptions to cases where the accused infringer had no knowledge of the patent. In addition, Chapter 5 demonstrates that 3D printable files will not infringe traditional patent claims directed to tangible objects. Moreover, the most commonly traded 3D printable file format will not infringe a computer-readable medium (Beauregard) claim. Attempting to alleviate some of the protection gaps for patent holders while balancing the needs of users, the chapter considers a novel theory of “digital patent infringement.”