Judges, lawyers, and scholars have long decried the high reversal rate district courts face in patent cases. Many have suggested greater district court specialization as a solution, and Congress in 2011 enacted legislation to promote such specialization. In this Article, Professors Lemley and Miller investigate the impact of a novel measure of a judge’s experience with patent cases—whether a district court judge has sat by designation on a Federal Circuit panel in a patent claim construction appeal—on the likelihood a district judge’s subsequent claim constructions are reversed.Their results might be thought to suggest a simple way to reduce the reversal rate in patent and perhaps other sorts of cases. But there is a catch: their evidence suggests this increased agreement is due to increased Federal Circuit trust in the decisions of individual judges who have sat by designation and not increased district judge understanding of claim construction. Personal relationships, not learning patent law, seem to explain why the reversal rate drops.