This chapter discusses ex post (after the event) and ex ante (before the event) inquiries. It begins by sketching two of the ex ante inquiry models that are encountered in the planning context. The first model involves an inquiry that takes place before the making of any decision whatever and the second involves inquiries that are taken in advance of any decision on the relevant matter being reached, as well as inquiries that are undertaken in the course of an appeal that is lodged against a decision. The chapter then considers the nature and purpose of ex ante inquiries and the right to know the opposing case, along with participation and procedure as they apply to inquiries. It goes on to examine ex post inquiries and the role of judges in holding such inquiries before concluding with an analysis of government accountability with respect to inquiries.