This chapter reviews empirical literature studying the patentability requirements. The chapter initially explores scholarship focused on whether a patent’s validity is empirically quantifiable. This literature attempts to discern indicators of patent validity and patent quality. The chapter then examines scholarship on the courts and how they evaluate a patent’s (or patent application’s) validity. These studies examine judicial and administrative outcomes and the content of such decisions reaching these outcomes with the goal of both quantifying a decision-maker’s attitude toward patentability and identifying the specific standards and analysis used in deciding patentability.