Since the events of Sept. 11, 2001, the world has become a different place. More attention than ever is being paid to the nation's vulnerabilities, and this has prompted officials at all levels to examine the tools available for ensuring the security of public utilities. The recent emphasis on making sure that public water supplies are safe has created the need for continuous monitoring systems and analytical techniques that can be used at the utility level to test for a variety of toxic materials in a short amount of time. States and colleagues provide a survey of continuous monitoring and analytical methods currently available to utilities for security purposes. This survey grew out of an investigation the Pittsburgh (Pa.) Water & Sewer Authority (PWSA) and the University of Pittsburgh School of Engineering conducted in order to identify feasible analytical responses to security concerns. This investigation included a literature search; discussions with personnel from various water utilities, water industry organizations, and regulatory agencies; and evaluation of several commercially available monitoring and analytical systems. The article also takes a look at the analytical measures PWSA uses to screen for possible contamination in response to threats or suspected tampering with its water system as well as during times of heightened security. Although these methods are limited and their results should be interpreted with caution, there are some techniques, such as acute toxicity testing, that can be useful. Includes 17 references, tables, figures.