The Board of Patent Appeals and Interferences (the BPAI) recently determined that arguments made for the first time in a reply brief will not be considered on appeal without “good cause.” In a recent precedential opinion, ex parte Atsuhisa Nakashima, the BPAI interpreted 37 C.F.R. § 41 as not requiring the BPAI to consider new reply brief arguments. In its principal brief, the applicant argued that the Examiner’s suggested combination would destroy the functionality of the primary reference and that the references were deficient with regard to an aspect of the claims at issue. The applicant included a new argument in the reply brief that there was no reason to combine the references because the result would be undesirable. The new argument was made without any stated reason as to why it had not been presented in the principal brief. The BPAI refused to consider the new argument, stating that “any argument not timely presented in the principal Brief [sic] will not be considered when filed in a Reply Brief, absent a showing of good cause explaining why the argument could not have been presented in the Principal Brief.” It is worth noting that a pending en banc Federal Circuit case, Hyatt v. Kappos, will consider the limits of new arguments and evidence that can be presented in appeals of BPAI decisions to a District Court under 35 U.S.C. § 145. The outcome of this case may impact an applicant’s strategy for selecting arguments and evidence to present at various stages of appeal.