Description:The reality of the post-September 11 situation forces the operators of water supply systems through the world to examine the security and safety of their systems, its vulnerability to intentional interference and sabotage with respect to quantity and quality of potable water. In assessing system vulnerability, there is an urgent need to develop emergency response plans providing ways and means for alternative water supply at the moment of system operation disruption, and system remediation and recovery after the attack. Security of Water Supply Systems: from Source to Tap presents the state-of-the art with a view to the future, conclusions from past experiences are highlighted and future developments are suggested in the field of drinking water safety.