The imperative of judicial deference is arguably the primary driver of the Supreme Court's prisoners' rights jurisprudence. Yet taken as a body, the cases in this area reveal no principled basis for determining when deference is justified, what forms it may legitimately take, or the proper limits on its use. Instead, the mere mention of "deference" has emerged as a catch-all justification for curtailing both the burden on prison officials to ensure constitutional prisons and prisoners' prospects for recovery even for arguably meritorious claims. The role of deference in prison law merits a longer and more in-depth treatment than I am able to offer here. This essay is simply a first cut at the issue. As such, it does three things. First, it identifies three main forms that deference takes in this area and provides examples of the deployment of each in the prisoners' rights cases. Second, it highlights moments in the PLRA cases where the Court has opted not to defer (thus seeming to reject strategies it freely employs elsewhere), and offers a preliminary hypothesis as to why this might be. Third and finally, it calls for a theory of deference for the prison law context, i.e., for the development of principles to guide judicial deference in prison law cases and to set appropriate limits on its use.