Cost of service and price cap are the two most popular strategies for regulating the prices charged by infrastructure monopolies that are too complex to be regulated by concession contracts. The choice between cost of service and price cap depends on whether maintaining the firm's ability to raise capital is more important than improving its technical efficiency. Regulatory agencies should not pursue either the financial or efficiency goal exclusively, however, and should avoid the confusion caused by the assumption of too much responsibility for goals that have little to do with the control of a monopoly.