There are many definitions of syndromic surveillance, but most highlight the use of ‘‘nondiagnostic’’ data—that is, information on possible health events before, or without, definitive laboratory identification of the pathogen. Unfortunately, there is confusion about the terminology, as the term had already been used to refer to surveillance based on clinical presentation. Clinical case definitions have long been used in surveillance, particularly for newly recognized diseases before laboratory tests have been developed, and they are used in the revised IHR. This approach has been used successfully in the smallpox and polio eradication programs and proposed for surveillance of emerging infections.18 Syndromic surveillance, as the term is currently used, by contrast includes a wide variety of other and nontraditional data sources. There has been an increasing interest in this type of syndromic surveillance, especially since 2001, when an important conference (supported by the Alfred P. Sloan Foundation) led to the formation of the International Society for Disease Surveillance (http://www.syndromic.org/) to advance research and development in the field. Although there is some general agreement about the data sources and methods that fall under the rubric of syndromic surveillance, definitions are often unclear. As Henning noted, ‘‘Specific definitions for syndromic surveillance are lacking, and the name itself is imprecise.’’28(p8) One widely cited definition comes from CDC’s document for evaluating public health surveillance systems for early detection of outbreaks; it defines syndromic surveillance as an investigational approach where health department staff, assisted by automated data acquisition and generation of statistical signals, monitor disease indicators continually (realtime) or at least daily (near real-time) to detect outbreaks of diseases earlier and more completely than might otherwise be possible with traditional public health methods.29(p2) Although this often involves automated data collection, which offers obvious advantages, it is not a requirement.