Petitioner KP Permanent Make-Up, Inc., and respondents (collectively Lasting) all use the term "micro color" (as one word or two, singular or plural) in marketing permanent cosmetic makeup. The Court accepts KPs claim that it has used the single-word version since 1990 or 1991. In 1992, Lasting registered a trademark that included the words "Micro Colors" under 15 U. S. C. §1051, and, in 1999, the registration became incontestable, §1065. When Lasting demanded that KP stop using the word "microcolor," KP sued for declaratory relief. Lasting counterclaimed, alleging, inter alia, that KP had infringed Lastings trademark. KP responded by asserting the statutory affirmative defense of fair use, §1115(b)(4). Finding that Lasting conceded that KP used "microcolor" only to describe its goods and not as a mark, the District Court held that KP was acting fairly and in good faith because KP undisputedly had employed the term continuously from before Lasting adopted its mark. Without enquiring whether the practice was likely to cause consumer confusion, the court concluded that KP had made out its affirmative defense under §1115(b)(4) and entered summary judgment for KP on Lastings infringement claim. Reversing, the Ninth Circuit ruled that the District Court erred in addressing the fair use defense without delving into the matter of possible consumer confusion about the origin of KPs goods. The court did not pointedly address the burden of proof, but appears to have placed it on KP to show the absence of such confusion.

Held: A party raising the statutory affirmative defense of fair use to a claim of trademark infringement does not have a burden to negate any likelihood that the practice complained of will confuse consumers about the origin of the goods or services affected. Pp. 4-12.

(a) Although §1115(b) makes an incontestable registration "conclusive evidence ... of the registrants exclusive right to use the ... mark," it also subjects a plaintiffs success to "proof of infringement as defined in section 1114." Section §1114(1) in turn requires a showing that the defendants actual practice is "likely to cause confusion, or to cause mistake, or to deceive" consumers about the origin of the goods or services in question, see, e.g., Two Pesos, Inc. v. Taco Cabana, Inc., 505 U. S. 763, 780. Thus, a plaintiff claiming infringement of an incontestable mark must show likelihood of consumer confusion as part of the prima facie case. This plaintiffs burden must be kept in mind when reading §1115(b)(4), which provides the fair use defense to a party whose "use of the ... term ... charged to be an infringement is a use, otherwise than as a mark, ... of a term ... which is descriptive of and used fairly and in good faith only to describe the goods or services." It is evident (1) that §1115(b) places a burden of proving likelihood of confusion (that is, infringement) on the party charging infringement even when relying on an incontestable registration, and (2) that Congress said nothing about likelihood of confusion in setting out the elements of the fair use defense in §1115(b)(4). It therefore takes a long stretch to claim that a fair use defense entails any burden to negate confusion. It is not plausible that Congress would have used §1114s phrase "likely to cause confusion, or to cause mistake, or to deceive" to describe the requirement that a markholder show likelihood of consumer confusion, but would have relied on §1115(b)(4)s phrase "used fairly" to give a defendant the burden to negate confusion. See, e.g., Russello v. United States, 464 U. S. 16, 23. Congresss failure to say anything about a defendants burden on this point was almost certainly not an oversight, since the House Trademarks Subcommittee refused to forward a proposal expressly