Abstract: On May 25, 2011, in Therasense, Inc. v. Becton, Dickinson & Co., the en banc U.S. Court of Appeals for the Federal Circuit fundamentally restructured the patent law doctrine of inequitable conduct. The court did so by holding that both intent and materiality are required for successfully claiming the defense, and that materiality must be proven by a but-for test, thereby limiting the scope of conduct covered by the doctrine. Although in making this change the court may have helped to curb the over usage of inequitable conduct, it did so by contradicting Supreme Court precedent. Thus, this Comment argues that the Therasense court overstepped its bounds and, in its attempt to limit the doctrine, may have unduly narrowed this equitable defense.