Most countries active in pharmaceutical innovation provide some sort of patent protection for new medical uses of known products. This provides market exclusivity, for example, when investigators find a new, non- obvious medical indication for a drug previously patented as a new, non-obvious molecule. Yet, despite clear policy importance of developing new treatments quickly and cheaply, surprisingly little is known about the scale and impact of these patents. Without more information, it is perilous for judges, policymakers and patent offices to presume they can propose or interpret rules on the validity and infringement of patents for new medical uses with reasonable chances of desirable social outcomes. How sought-after are new medical use patents? Is their popularity waxing or waning? Who is benefitting from this government- granted market protection? What types of claims are being used to protect these inventions? Is it true that serious disadvantages would follow if such patents were harder to obtain or to enforce? Should they be easier to obtain and enforce? Who will be the winners and losers if rules on acquisition and infringement are adjusted?