Large water resources development projects have a strong impact on the river basin as a whole. It is for that reason that the studies not only involve technical experts like geologists, hydrologists and engineers but also social-geographers, ecologists and economists. But how are these experts involved? Why have even projects sponsored by the very careful World Bank so often encountered implementation, operational and social problems? This article suggests that involving these different experts in a useful way is difficult and asks for skills and attitudes that were not needed for less complex endeavours. Based on the experience with the Dutch Delta works, this contribution describes the most important qualities of the organization needed for fruitful multidisciplinary work. These qualities are (1) openness, meaning no secrets on important issues of the project, (2) a widely accepted goal for the project and (3) a sound project management, instead of the commonly used hierarchical management.