The Mississippi is one of the most rigorously controlled and engineered rivers in the world, yet in the summer of 1993 it suffered the worst flooding in its history. Fundamental questions are now being asked about whether river engi­neering really works or whether trying to tame a river actually makes floods worse. Answers must be found soon, because Bangladesh is about to launch the most ambitious flood control project ever attempted. If the engineers get it wrong, it will be disastrous.