Abstract: Discretion is examined as a feature of the design of rule-guided systems. That is, given that rules have to be administered by some group of persons, called adjudicators, and given that their goals may be different from society's (or a relevant organization's), when is it socially desirable to allocate discretionary authority to the adjudicators and, if so, to what extent? The answer reflects a trade-off between the informational advantage of discretion - that adjudicators can act on information not included in rules - and the disadvantage of discretion - that decisions may deviate from the desirable because adjudicators' objectives are different from society's. The control of discretion through limitation of its scope, through decision-based payments to adjudicators, and through the appeals process, is also considered.