The Program for Monitoring Emerging Diseases (ProMED-mail) reports on outbreaks of diseases of infectious or toxic etiology, whether natural or intentionally released, that affect humans. Open to all sources, free of political constraints, and available to users free of charge, ProMED-mail exploits the speed and ubiquity of the Internet to serve as an early warning system for the detection of emerging disease outbreaks. ProMED-mail monitors diseases of plants and animals of agricultural importance in addition to zoonoses because of their key role in disease emergence. Reports are carefully screened for validity and are placed in an appropriate context by commentary and references from a panel of expert moderators. Reports are then posted to the Web and sent by e-mail to >32,000 subscribers in >150 countries.