Fixing Double Patenting 

40 Pages Posted: 12 Jul 2024

Date Written: July 05, 2024


The U.S. patent doctrine of “double patenting” allows an inventor to obtain many patents on obvious variants of the same invention as long as they file a “terminal disclaimer” agreeing that all of these patents will expire simultaneously. Two recent limitations on double patenting practice have led to vigorous protest from the patent bar. First, the Federal Circuit held that in In re Cellect that patents tied by double patenting must expire on the same day even if one of the patents has received a patent term adjustment giving it a more-than-twenty-year term. Second, the USPTO proposed that terminal disclaimers include a commitment to not enforce the patent if any claims in the patent to which it is tied are found to be obvious or not novel.

In this article, we argue that the outcry over these decisions is unwarranted. We empirically show that double patenting is growing, with terminal disclaimers now being filed for over 15% of all patents, over 50% of litigated patents, and over 60% of patents covering FDA-approved drugs. The proliferation of patents on slight variations of the same invention has increased the burden on patent examiners and the costs to innovative firms of evaluating, licensing, and litigating existing patents. Reducing abuses associated with double patenting by preventing unjustified term extensions and lowering the costs of challenging invalid patents makes good policy sense. Indeed, the USPTO and the courts could do more to restrict double patenting, including banning the practice altogether. Doing so would allow inventors and the USPTO to focus on important new inventions rather than trivial variants of existing ones.

Keywords: Patent, Double Patenting

Suggested Citation

Lemley, Mark A. and Ouellette, Lisa Larrimore, Fixing Double Patenting  (July 05, 2024). Available at SSRN: or

Mark A. Lemley (Contact Author)

Stanford Law School ( email )

559 Nathan Abbott Way
Stanford, CA 94305-8610
United States

Lisa Larrimore Ouellette

Stanford Law School ( email )

559 Nathan Abbott Way
Stanford, CA 94305
United States


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