Likelihood of confusion in the Federal Circuit
(1) The similarity or dissimilarity of the marks in their entireties as to appearance, sound, connotation and commercial impression.
(2) The similarity or dissimilarity and nature of the goods or services as described in an application or registration or in connection with which a prior mark is in use.
(3) The similarity or dissimilarity of established, likely-to-continue trade channels.
(4) The conditions under which and buyers to whom sales are made, i. e. “impulse” vs. careful, sophisticated purchasing.
(5) The fame of the prior mark (sales, advertising, length of use).
(6) The number and nature of similar marks in use on similar goods.
(7) The nature and extent of any actual confusion.
(8) The length of time during and conditions under which there has been concurrent use without evidence of actual confusion.
(9) The variety of goods on which a mark is or is not used (house mark, “family” mark, product mark).
(10) The market interface between applicant and the owner of a prior mark:
(a) a mere “consent” to register or use.
(b) agreement provisions designed to preclude confusion, i. e. limitations on continued use of the marks by each party.
(c) assignment of mark, application, registration and good will of the related business.
(d) laches and estoppel attributable to owner of prior mark and indicative of lack of confusion.
(11) The extent to which applicant has a right to exclude others from use of its mark on its goods.
In re E. I. du Pont de Nemours and Co., 476 F.2d 1357, 177 USPQ 563 (CCPA 1973).