Abstract:The Mar del Plata International Water Conference provided the first global assessment of the water sector. It was found that in most developing countries the state of water supply and sanitation services were deplorable. Consequently, a call for concerted action to improve coverage and efficiency of the water supply and sanitation sector was launched. This call resulted in the International Water Supply and Sanitation Decade (1981)(1982)(1983)(1984)(1985)(1986)(1987)(1988)(1989)(1990). The Decade provided important lessons concerning effective methodologies to improve the state of the WSS sector. The paper discusses why the poor state of the water supply and sanitation conditions still tend to be the greatest development failure during the 20th century. The recipe for success was there, and the money was there. So, why were governments and big donors like the World Bank refusing to apply the lessons from the Decade? The basic conditions for success are spelled out, and some successful cases are used to illustrate these. The conclusion is that change is possible but that civil society organizations have to be empowered to make governments -feel the heat‖ and spend more money on water and sanitation, and to spend it more wisely.