How many bites at the apple does the Patent Trial and Appeal Board allow? That is, are parties limited to a single invalidity challenge to a patent claim in inter partes review, or are parties able to file serial challenges against a claim? While the statutes governing this important question may be open to interpretation on this fundamental question, the PTAB has adopted a decidedly permissive approach. This article reviews the statutory and legislative background and the empirical facts of current practice, and offers some strategic pointers for offense and defense at the PTAB.