After half a century of monitoring voluntary reports of medical product adverse events, the Food and Drug Administration (FDA) has launched a long-term project to build an adverse events monitoring system, the Sentinel System, which can access and evaluate electronic health care data to help monitor the safety of regulated medical products once they are marketed. On the basis of experience gathered through a number of collaborative efforts, the Federal Partners' Collaboration pilot project, involving FDA, the Centers for Medicare & Medicaid Services, the Department of Veteran Affairs, and the Department of Defense, is already enabling FDA to leverage the power of large public health care databases to assess, in near real time, the utility of analytical tools and methodologies that are being developed for use in the Sentinel System. Active medical product safety surveillance is enhanced by use of these large public health databases because specific populations of exposed patients can be identified and analyzed, and can be further stratified by key variables such as age, sex, race, socioeconomic status, and basis for eligibility to examine important subgroups.