In 1970 the Haringvliet estuary of the rivers Rhine and Meuse was closed off from the sea by a dam with outlet sluices to protect the land from storms at sea. This resulted in (he creation of a freshwater lake, suitable for agricultural water supply and drinking water. However, the change of an open estuary into a semi-stagnant lake had many negative ecological effects: loss of natural habitats, bank erosion, accumulation of polluted sediments and the disappearance of a natural transition zone between the estuary and the sea. Hence many characteristic species disappeared. In the 1980s public demand for nature in the Netherlands grew and agricultural importance declined. The ecological degradation was more and more recognized as a problem. In 1988 the government decided to investigate whether it was possible to change the management of the Haringvliet sluices. The conclusion was that alternative management, can lead to a major rehabilitation of the Rhine-Meuse estuary since natural processes will return. In 1998, the government decided to strive for an alternative management regime. The first step will be to put the 'sluices ajar' in 2008. This article gives an overview of questions arisen and learning points encountered while implementing the alternative management of the Haringvliet sluices.