Many countries are weighing urgentreforms to bring safe water supply and sanitation (WSS)services to hundreds of millions of poor city dwellers. Pastreforms, unfortunately, have often ignored consumerpreferences and perceptions, resulting in overly optimisticprojections of the revenue potential of reform projects.When revenues fall short, private partners may seek torenegotiate their contract, resulting in tariff increasesand other changes that increase project costs across theboard. Such situations can undermine political commitment toreforms in general and to Private Sector Participation (PSP)in particular. Understanding consumers can help avoid suchsituations. Different groups of consumers have distinctpreferences and perceptions that may influence theirdecisions about new water systems. Unfortunately, studies ofconsumers' water-related preferences are often deferredbecause collecting data takes time and costs money. Oftenthere is pressure to complete reforms quickly sometimes totake advantage of a political opportunity so the necessaryresearch is not done. In other cases, the challenge ofincreasing efficiency and improving governance may seem sodaunting that the specific interventions required to makereform beneficial to the poor may be overlooked orconsciously deferred.