One possible aim of epistemology is to advise cognizers on the proper choice of beliefs or other doxastic attitudes. This aim has often been part of scientific methodology: to tell scientists when they should accept a given hypothesis, or give it a certain degree of credence. This regulative function is naturally linked to the notion of epistemic justification. It may well be suggested that a cognizer is justified in believing something just in case the rules of proper epistemic procedure prescribe (...) that belief. Principles that make such doxastic prescriptions might thereby "double" as principles of justification. In the first part of this paper I contrast the regulative conception of justification with another, equally tenable, conception. Then, after noting a fundamental worry about the applicability of the regulative conception, I proceed to lay it out in more detail. The regulative justificational status of a doxastic attitude for person S at time t depends upon (a) the right set of doxastic instructions and (b) the states S is in at (or just before) t. (shrink)