In this paper, we show that there are important differences across patent examiners at the U.S. Patent and Trademark Of!ce (USPTO), and that these relate to the most important decision made by the USPTO: whether or not to grant a patent. We !nd that more experienced examiners, and those who systematically cite less prior art, are more likely to grant patent applications. These results are not encouraging as a matter of public policy. But they do point to human resource policies as potentially important levers in patent system reform.