The new theories of regulation show how to achieve the best possible results if the regulatorlacks information. This paper has first presented various simple regulatory mechanisms, in particular the Vogelsang-Finsinger iterative mechanism and Shleifer’s yardstick regulation. Unfortunately, in practical applications of these simple mechanisms the regulated utility will be able to dodge the regulator’s intentions by strategic behavior. This has lead us to a treatment of informationally-demanding regulatory mechanisms which are incentive-compatible and, therefore, strategy-proof. Unfortunately, however, the regulator must be extremely well-informed if he wants to apply this sort of regulation: except for the actual realizations of a cost or demand characteristic and the effort of the manager, he must be perfectly informed about the situation of the regulated public utility. This must be the main reason why in practice the simple price-cap regulation prevails, in particular, the RPI-X type of price regulation. Obviously, it represents an acceptable compromise between not too high information problems and not too high incentives for managerial strategic behavior.