Abstract: Legal advice is the information that lawyers provide to clients about the nature of legal rules, about the probability and magnitude of sanctions for their violation, and about litigation and legal procedure. The chief questions addressed here are how legal advice helps clients and how, or whether, it advances social welfare. The analysis distinguishes between two major types of legal advice: ex ante advice, obtained when a party is contemplating an action with possible legal consequences; and ex post advice, secured after a party has acted or someone has been harmed, which is to say, at the stage of possible or actual litigation.