Section 37 of the Lanham Act vests courts with the power to order the Director of the U.S. Patent and Trademark Office (PTO) to cancel trademark registrations. 1 This power to “rectify the register”2 is discretionary, and since the act’s enactment in 1946, courts have routinely granted cancellation requests when the trademark’s invalidity was established in the trial court proceedings. However, that is not always the outcome. Some courts refuse to exercise their power to rectify the register under section 37 even with a proven and valid basis for cancellation. This article examines cases where the district courts refused to cancel invalid trademarks even though a basis for cancellation had been established. In some cases, the appellate courts have reversed, holding that this was an abuse of discretion. In others, the Courts of Appeals have affirmed the refusal to cancel. Why the difference? The distinguishing fact appears to be that in cases where cancellation was ultimately ordered, the party seeking cancellation affirmatively sought cancellation via a cause of action—typically a counterclaim in an infringement suit. In cases where cancellation was ultimately rejected, the common theme seems to be that the party did not request cancellation as a claim, but instead requested cancellation as a remedy in a motion.