Following the attacks of September 11, 2001 the drinking water industry like many other sectors of our society realized the possibility that they could potentially become the target of malevolent acts. The most serious concern is that an individual or group might intentionally contaminate the public water supply. From an analytical perspective this new concern introduced two challenges. The first is the need to be able to conduct rapid analyses, perhaps at the scene of a suspected contamination event, to obtain preliminary, presumptive information that can help emergency responders determine, in a timely manner, whether a harmful substance had indeed been introduced into the water. The second challenge is the need to develop a robust and sensitive continuous online monitoring system that can detect harmful chemicals, microbes, or radionuclides that may have intentionally, or even accidentally, found their way into the municipal water system. This paper summarizes the current state of technology in these two areas and describes some of the shortfalls where future development is needed.