Abstract: Chevron v NRDC may well be the most important case in all of administrative law. It establishes a general principle, which is that agencies may interpret ambiguous statutory provisions, so long as their interpretations are reasonable. That principle is now under serious pressure. If the Court abandoned it, how would Chevron itself be decided? There are five possible approaches: (1) textualism; (2) purposivism; (3) resort to canons of construction; (4) use of Skidmore deference; and (5) validation of the agency’s decision, on the ground that no statutory provision prohibited it. In the context of Chevron, (1) and (2) run into serious problems, but (3), (4), and (5) are promising. The discussion suggests some general lessons for statutory interpretation and administrative law, and offers some cautionary notes for those who want to abandon the Chevron framework. Abandoning that framework would introduce high levels of confusion in the lower courts and the Supreme Court itself, and in all probability, the framework that would ultimately replace it would turn out to look a fair bit like that in Chevron itself.