In Dayco Products, Inc. v. Total Containment, Inc., 329 F.3d 1358 (Fed. Cir. 2003), the Federal Circuit was confronted with the question of which “materiality” standard should be employed in inequitable conduct determinations for patents prosecuted under the 1992 amendment to C.F.R. § 1.56 (“Rule 56”), — the pre-1992 “reasonable examiner” standard (whether a reasonable examiner would have considered the information in question important in deciding whether to allow the application), or the standard defined by the amended Rule 56 (whether the information in question establishes a prima facie case of unpatentability or refutes or is inconsistent with an applicant’s position supporting patentability)? In a case of first impression, the Federal Circuit left the question open by declining to mandate which standard should apply, and side-stepped the issue because an analysis of the facts under both standards yielded a same result. The court did, however, answer another question of first impression in deciding that a rejection of substantially similar claims by another examiner in a co-pending U.S. application is material, and must be disclosed during prosecution.