Professor J. Thomas McCarthy: "What is the 'Zone of Natural Expansion' Doctrine?"

Professor McCarty, renowned author of McCarthy on Trademarks and Unfair Competition, cast a critical eye on two recent decisions (one from the CAFC, one from the TTAB) discussing the zone-of-natural-expansion "doctrine." He asks, "what is it?" "How does it fit with the familiar 'related goods and services' rule and the test of likelihood of confusion?" The professor concludes that it is not a "doctrine" at all. "Neither the Federal Circuit nor the T.T.A.B. has the authority to replace the statutory likelihood of confusion test with a 'doctrine' of 'zone of natural expansion' to decide issues of priority and entitlement to registration."

What is It? The "zone of natural expansion" argument has sometimes been discussed in both court litigation and U.S.P.T.O. inter partes cases. But unlike infringement litigation in court, the issue in T.T.A.B. cases is not enjoining an intervening user. The issues are priority, ownership and registration rights. Recently both the Federal Circuit and the Trademark Trial and Appeal Board applied and discussed at length the “zone of natural expansion." But what is it? How does it fit with the familiar “related goods and services” rule and the test of likelihood of confusion?

The basic theory seems to be that use of a mark on goods or services in the A market (for a hypothetical, assume it’s ALPHA auto tires) has an exclusive “zone of natural expansion” that extends to goods and services in the B market (for example, bicycle tires) that are encompassed within a zone that buyers would usually expect a mark in the A market to expand into. It is usually used in a situation where a junior intervening user starts use of a similar mark in the B market (hypothetically, assume it’s ALFAH bicycle tires). Then the senior user later expands into that market (ALPHA bicycle tires). In this hypothetical example, the senior user of ALPHA argues that there is a conflict because buyers would think that bicycle tires are in a "natural expansion zone" for ALPHA auto tires.

But if we change the facts of the hypothetical and have the intervening use be ALFAH for use on vehicle collision avoidance software, it is likely a judge would find that ALPHA’s later expansion from auto tires to use on vehicle collision avoidance software is not a “natural expansion.” If the decision rests solely on using the “zone of natural expansion,” then the senior user’s later expansion to ALPHA vehicle collision avoidance software is likely an infringement of the intervening use by ALFAH on the same kind of software. In the U.S.P.T.O. ALFAH would be deemed “senior user” and entitled to a registration for vehicle collision avoidance software.

Federal Circuit and Trademark Board Use of “Zone of Natural Expansion.” In March 2025 the Federal Circuit in the Dollar Financial case [TTABlogged here] held that: “We decline to expand the scope of the zone of natural expansion doctrine and affirm that the doctrine may only be used defensively to prevent junior users from registering similar marks on goods in a senior user’s zone of natural expansion.” But the meaning of the court’s “defensive” versus “offensive” distinction is both unclear and unhelpful. It needs explanation. On April 11, 2025 the T.T.A.B. in Streeter v. GuideOn Education [TTABlogged here] applied the Dollar Financial approach, referring to the petitioner’s “fallback position” of natural expansion. In both cases, the judges held that the senior user had not proven that it was entitled to prevail.

It is not clear what the court meant by a forbidden “offensive” use of the natural expansion concept. Apparently it means that once it has been proven that the intervening use is on unrelated goods or services, then the senior user cannot use the natural expansion argument to change that situation. Although the court did not say so, this necessarily implies that the intervening use on unrelated goods or services was not likely to cause customer confusion with the senior user.

“Zone of Natural Expansion” is Not a “Doctrine.” Both the Trademark Board and the Federal Circuit have continually referred to the concept of zone of natural expansion as a “doctrine.” This creates the incorrect impression that it is a freestanding rule to determine if there is a trademark conflict and priority independent of the statutory test of likelihood of confusion of sponsorship, affiliation or connection. But "zone of natural expansion" is not a “doctrine.” It is an argument that the goods or services are related and confusion is likely. The “doctrine” is the statutory test of likelihood of confusion.

As discussed in my treatise at §24:20, the “natural expansion” argument is just a way to argue that there is a likelihood of confusion of source or sponsorship in a particular factual situation. If the “intervening” junior use was likely to cause confusion when commenced, it was an infringement. In that case, the senior user has the right to enjoin such use, whether the senior user had in fact already expanded itself or not. Conversely, if the “intervening” use was not likely to cause confusion when it began, then the intervening user is not an infringer. If the senior user later expands to that unrelated line, then it is an infringer in that line of goods or services.

Conclusion. The “zone of natural expansion” is not an independent rule to resolve a conflict between trademark uses. The “doctrine” that is required to decide these cases of an intervening use is the §2(d) statutory test of likelihood of confusion. The focus should be on consumer perception, not on a judge’s decision as to whether an expansion is “natural” or not. Neither the Federal Circuit nor the T.T.A.B. has the authority to replace the statutory likelihood of confusion test with a “doctrine” of “zone of natural expansion” to decide issues of priority and entitlement to registration.

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TTABlogger comment: What he said!

Introductory Text Copyright John L. Welch 2025.