Mining text for real-time syndromic surveillance usually requires a comprehensive knowledge base (KB), which contains detailed information about concepts relevant to the domain, such as disease names, symptoms, drugs and radiology findings. Two such resources are the Biocaster Ontology (1) and the Extended Syndromic Surveillance Ontology (ESSO) (2) . However, both these resources are difficult to manipulate, customize, reuse and extend without knowledge of ontology development environments (like Protégé) and Semantic Web standards (like RDF and OWL). The cKASS software tool provides an easy-touse, adaptable environment for extending and modifying existing syndrome definitions via a web-based Graphical User Interface, which does not require knowledge of complex, ontology-editing environments or semantic web standards. Further, cKASS allows for*indeed encourages*the sharing of user-defined syndrome definitions, with collaborative features that will enhance the ability of the surveillance community to quickly generate new definitions in response to emerging threats.