Abstract: This Article presents a systematic consideration of how administrative law doctrines apply to banking supervision, an unusual form of administrative practice that rests on an iterative relationship between banks and supervisors. First, it describes the rationales for, and process of, bank supervision. Second, this Article uses recent administrative law arguments lodged by banking interests against key supervisory practices as the springboard for an analysis of why our largely “trans-substantive” administrative law can be problematic in the context of specific mandates given by Congress to administrative agencies. It argues that courts considering how administrative law doctrine applies to agency practices must contemplate more fully the substantive law the underpins the mission and organization of the agency. When these statutory provisions are taken appropriately into account, arguments that supervisory practices are consistent with administrative law requirements are substantially strengthened. Third, this Article demonstrates how even a more tailored application of contemporary administrative law doctrines would miss a critical feature of banking supervision—that it is premised on an ongoing relationship between banks and supervisors. Judicial review of agency action usually focuses on discrete agency actions, thereby eliding this critical fact. As a result, administrative law doctrines such as the “practically binding” test for agency guidance are peculiarly inapposite. Lastly, this Article offers a tentative proposal for shifting the administrative law review of supervisory actions to focus on how banking agency processes manage the iterative nature of the supervisory relationship.