An interference is a proceeding in which the Board determines which, if any, of the owners of conflicting applications (or of one or more applications and one or more registrations that are in conflict) is entitled to registration. See 15 U.S.C. §§1066, 1068.
An interference can be declared only upon petition to the Director. However, the Director will grant such a petition only if the petitioner can show extraordinary circumstances that would result in a party being unduly prejudiced in the absence of an interference. 37 C.F.R. §2.91(a). The availability of an opposition or cancellation proceeding ordinarily precludes the possibility of undue prejudice to a party. Thus, a petitioner must show that there is some extraordinary circumstance that would make the remedy of opposition or cancellation inadequate or prejudicial to the party’s rights. Interferences are generally limited to situations where a party would otherwise be required to engage in successive or a series of opposition or cancellation proceedings, and where the issues are substantially the same. See In re Family Inns of Am., Inc., 180 USPQ 332 (Comm'r Pats. 1974).
The following matters are not subject to interference: (1) registrations on the Supplemental Register; (2) applications for registration on the Supplemental Register; (3) registrations under the Act of 1920; and (4) registrations of marks that have become incontestable. 37 C.F.R. §2.91(b).
See TMEP §§1208.03 et seq. and TBMP Chapter 1000 for more information about interferences.