This article examines the effects of systematizing tendering procedures when awarding public service concessions. The opening up of the water supply industry to competition is used by way of illustration. Results show that arguments in favour of systematization are not robust when focusing solely on the expected benefits of the liberalization process. The peculiarities of the contract relationship in the delegation of public services, the mobilization of specific assets, and the long duration and incompleteness of the contracts invalidate this type of argument and expose public authorities to the opportunism of operators. Copyright 2003 CIRIEC.