The role of the health professional in supporting the national passive surveillance system is essential, as the first hint of a potential problem usually originates with the astute clinician who reports a case to the appropriate source. The investigation that resulted in the voluntary withdrawal of rotavirus vaccine was triggered by nine reports to VAERS of intussuception, eight of which had occurred within 1 week of the first dose of this vaccine. Health professionals have access to the most complete information related to adverse events experienced by their patients. Any index of suspicion that a serious event or death may be related to vaccination is reason for the health professional to submit a VAERS report. Determination of whether an event was caused by the vaccine is not a prerequisite for filing a VAERS report. When in doubt, providers should report to VAERS. VAERS solicits reports for all events temporally related to vaccination, some of which may be coincidental and some of which may merely indicate a change in the frequency of expected events. Post-marketing surveillance relies on health professionals to report suspicious events, thus improving the quality of reported data and contributing significantly to safeguarding public health. Recommendations for healthcare professionals to report to VAERS recently have been incorporated into the Standards for Pediatric Immunization Practices, which are endorsed by multiple professional organizations. Despite the limitations of spontaneous reports, VAERS provides vital information of clinical importance. The identification of signals in adverse event surveillance may initiate further investigation of potential problems in vaccine safety or efficacy, and facilitate subsequent dissemination of safety-related information to the scientific community and the public. This process begins with voluntary submission of reports of possible vaccine-associated events to VAERS by the informed and conscientious health professional.