The Federal Circuit has been reversing lower District Court decisions on claim construction at an alarming rate. Recent cases have been statistically analyzed to determine the most common errors committed by the District Courts. The results indicate that litigants cannot expect much certainty until they reach the Federal Circuit on appeal. Fortunately, most decisions by the lower courts are summary judgments, allowing litigants to get to the Federal Circuit quickly while avoiding the expense of trial. Federal Circuit opinions on claim construction have also been legally analyzed and recommendations will be presented to avoid narrowing claim construction, both in the preparation of applications and in prosecution.